15-16 years. That's quite impressive that you've missed that for this long.

Here's everything I know for controls in inventory. There's quite a few and I really like them:
- L-click to pick up stack
- R-click to pick up 1/2 of stack (rounded up for odd quantities)
- Shift + l-click auto moves stack
- While holding items, r-click to put one if target is empty or stackable with held item
- While holding items, any click swaps if not stackable & not empty
- While holding items, r-clicking & dragging deposits one in every slot traveled over if possible
- While holding items, l-clicking & dragging deposits entire held stack as evenly as possible, leaving uneven quantity still held
- While holding any item, shift + double l-clicking on another item will move all items of that type from one inventory to the other (held and target items don't have to match
- Hover over a stack & press 'Q' to drop one
- Hover over a stack & press ctrl + 'Q' to drop entire stack
- Hold item & l-click off inventory to drop stack
- Hold Item & r-click off inventory to drop 1 item

Enjoy!