If you think of some of your purchases as "experiences" rather than things, it feels better.  You might go on an outing and spend a few bucks on lunch, an admission to something, etc. that you'll never see again.  Same with art supplies.  You bought the supply so you could experience it.  Some of the art supply experiences, you will revisit, some you won't.  Sell it and forget it.  Healing with art means not letting your supplies stress you. Just a thought.  Interesting video!

Box up the art supplies you don’t love and drop them off for your local middle school art teacher. They will be a huge blessing and will take the burden/guilt away from you. If the art teacher can’t use them in class they may know a budding artist that would CHERISH them. As artists we often operate from a point of scarcity thinking that we may need a supply in the future. Let it go and bless someone else now and open you up for future things.

I am also a migraine person who can be instantly triggered by certain smells.  When you described how it smelled it reminded me of how things that trigger me smell.  A triggering smell seems to linger in my nostrils for days. No filter, mask, or fan will prevent this since once I am sensitized to a smell it is all over.   To avoid this in my art supplies, I really limit what I use and prefer watercolors.  I have saved a lot of pain and money by being VERY strict with myself by buying only the high-quality brands that are "safe".  The sooner those are out of your house, the better.  Just give them to someone or a school.

I like to take my soft pastels, shave some off into a small mixing dish and add medium.  They create beautiful glazes and transparent colors!

I've actually really come to be grateful that I have art supplies that I don't really like as much. It allows me to think of ways that I can still use them to experiment and practice with and just try stuff out. Like "Ooh, I wonder what happens if I use this pen with water color?" or "Hmm, I normally wouldn't use these colors together, but let's see what it looks like!" Even made a little scrappy sketchbook that I can switch out the pages as I like with different kinds of paper, old scribbles etc. to just play in. ^^

It’s like when we are snowboarding in less than ideal conditions. You can complain and have a lousy day or use it as an opportunity to hone your skills. Enjoy the adventure.
Use unfavorites to hone skills. Just use for ten minutes during unfavorites time. Skill building. If you find it’s not having any benefit at all then give it away. Don’t leave it in your space bring the object of your dissatisfaction 🙂

For the journal with the thin pages, gesso will cover up the ink leakage and if you want to watercolor over it, you can use watercolor ground. It isn't optimum for watercolors; however, it is great for acrylic or ink sketches.

1. If all else fails donate to a school.
2. I use cotton gloves due to hating the feel of certain media and throw into wash.
3. Use wax paper between oil pastel & other paper.
4. Not sure about hypersensitivity of smells. Do you keep a fan in basement? Wearing a mask?
5. Does pouring medium work as a sealant?
😊

With your "colour studies" sketchbook I do wonder if it might be worthwhile trying to turn it into an area where you work with a limited colour palette? It could help achieve similar goals (finding out what colours look like when they're mixed together) but be more engaging because you're doing it with the intent of making mini paintings/studies. Also it's good to see purchases from before this year because it might be that a supply that seemed to be good deteriorates after some time, or you find that it's not as great as you initially thought 🙂

I like what another commenter said about these purchases being experiences rather than things. Some purchases are mere whims that you buy spur of the moment, but it sounds like you had plans for many of these supplies and they just didn't work out. But how will you know unless you try? As others said, you could donate these to your local school, they would be glad to have them. Or check on the return policy from Jackson's. My local art store will let me return things, even if I've used them.

It might be worth taking a look at the ingredients lists on the substances that have odors and/or cause migraines; perhaps there is one (or more) common compound that you would know to avoid.  Such compounds may vary by whether you’re dealing with a paint vs. a medium, etc., so it could take some work to suss out.  Also agree with the comment about viewing buying new supplies as an experience. The soft pastels were a great example of this — how could you know you wouldn’t like the chalkiness until you tried it? (We do this at restaurants, too, right?) I’d also suggest to folks not to be afraid to return items that don’t work for you (migraine-inducing) or aren’t as advertised (ShinHan paints).  Most reputable stores have good return policies — but it does require using the product right away and making a reasonably rapid judgement — setting it aside for weeks or months can result in the refund period expiring.

I’m sure near where you live there are a lot of artists that would love to receive some of these supplies. For free or for a lower price. I wish I could know someone that didn’t like some of their art materials. Many times I have to choose between paper or whatever and medicine. Or food. 🤷🏻‍♀️
When I don’t like something - which of course happens to all with us - I usually give them. My 2 y old niece and 7 y old nephew have a lot of art materials because of this. I have a 14 old niece that most of her art materials at first she got because I couldn’t stand the smell of them. She didn’t feel anything. So I gave them to her. I think that it’s better than the materials go to waste.

You can use the sketchbook as a journal for new art supplies that you buy and test out. I have one just for that. You can then use it as reference when buying new art supplies. That also lets you know what you tried and have not tried

As many people have said, you can sell or donate the art supplies and it will make someone else very happy.
As for buying supplies and it just not clicking, that is just something that happens. Whether it is with clothes, shoes, or art supplies, sometimes we try something and it's just not for us. If we never try we will never know. You were brave enough to try things outside your comfort zone and it's okay if you didn't like them or they didn't suit you. It's all a part of life.

Edit: Regarding acrylics, some brands do have a scent and even if it's not strong they do affect people with sensitivities. I'm sorry that the acrylics that you enjoy trigger migraines. It always sucks when stuff like that happens.
Regarding the oil pastels, I support the suggestion of others to try Mungyo or Caran d'ache. Also, you can make envelopes out of wax/baking/parchment paper. They will help protect your artworks. My favourite solution is a binder filled with sheet protectors that I put my oil pastel paintings in. The Sennelier oil pastel fixative is another good solution, but please only use outside to help prevent exposure to the fumes if you do.

To vanish with gloss medium and avoid brush marks,  add 50/50 with water. Brush over a thin layer, wait until it is completely dry and repeat. You can add more layers if you want. It is important to let it completely dry between layers or it can go cloudy.

The Shinhan watercolour is great. You can mix it with some white gouache to get more pastelly colours and the shade that you want. There's a decent bunch of primary pastel colours there.

I think you’re overthinking it. Just use it for something. Even if it’s to sketch out an idea. Just rotate through your unfavorites until they’re used up and you can move on

A tip for using heavy body paints for paint pouring - mix the paint with a little bit of water or regular medium to thin the paint down a bit before adding the pouring medium. I have a mixture of heavy and soft body paints and they do play well if you experiment a but with water or other medium ratios.

We need more videos like this one. Thank you

I use gloss medium mixed with water as an isolation coat before varnishing and also between some layers of paint.  I mix maybe a 1/5 ratio of medium and water, it is very milky thin and does not leave brush strokes. If it does leave brush strokes, the mix is too thick, just add a little more water.