Is it possible to change the priority of the place for picked up item to something like this:

1. A stack in the toolbelt (if it exists).
2. A stack in the inventory (if it exists).
3. Hand (current empty toolbelt slot).
4. If hand is holding something else and allows picking an item up: first empty inventory slot.

The most common examples of "why" would be:

• Inability to take all stuff from shelves without having enough free slots even if the items on them are stackable (like bowls, usually you'll need only 2 slots, butt up to 8 with this mod).
• Unnecessary filling up empty slots, when player set a "dedicated" slot for this specific item (like setting 5th slot for torches, but picking them up with another slot selected).

I think there is already a mod which acts like this, but it has weird interactions with piles: they blink on any add/pickup action, and make multiple sounds on interactions instead of one.

If you haven't figured it out already, there is a setting for that in the config. HoosierDaddy

Would be very useful if it were only storage interactions. As is, when collecting stuff in the wild, I've got to select what I'm planning to collect via R-Click (copper, sticks, flint, etc.) or it fills up my formerly empty hand, and I have to move it to the stack in inventory. Considering how often I interact with storage vs. how often with stuff on the ground, it's just too much extra work.

If it stacked onto an inventory stack if one existed, that would be awesome.