Giving this my 2 cents. I personally believe the hotbar is a hot mess right now, and I have 2 ideas to fix it.
1. You can "favorite" items where you can assign an item to have priority on a hotbar slot.
2. The hotbar no longer automatically gets filled by items in your inventory. You have to manually set what items go into your hotbar and which slot.
Viewing post in Voices of the Void 0.8.2 feedback
Personally speaking I both love and hate that hotbar gets auto-filled. Sometimes, it's very useful to switch to things you've just used, but sometimes, especially when you collect trash - important items get shifted away.
I think that having both - an auto-fill, and an option to "favorite" items would be the best.