Once more:
We have tab-wise sorting.
PoE has merging.
Now you can do it in many many different variants depending on how your tabs are programmed and generally handled.
For example you got 5 free tabs which are in Legacy? Mark them which tells the system ‘put stuff in here’, then click ‘transfer’ and the system starts. 2x3 item? Enough space? Yes? push over… repeat until no more space. Does it fail to put one into a tab? Next tab, repeat until no items are left or the tabs run out.
Easiest and messiest solution, works with half-filled tabs, full tabs… whatever. Same way as to how pickup of items into the inventory works as that needs to see ‘is the space to put it there existing?’. So not much difference.
We can also theoretically expand on that system and let it sort specific item types, bases, affixes… whatever you can usually sort out dump into their respective tabs, similar to the loot filter options after all. All possible.
Much work? Sure.
Impossible? Don’t even start, obviously it’s possible.
Does it remove the ‘remove only tabs’? No… but that was never the goal, I specifically spoke about ease of usage for moving things over, period. We don’t need to talk about auto-merger which happen without player input and choice, those are shit, those don’t work, those shouldn’t even be thought about since they’re obviously failed features.