Unfortunately they removed this essential function because reasons. What reasons? Buckle up, this is going to get bumpy.
The lead dev., Dennis Douthett, and his team thought no one used it and I can’t fathom why they didn’t know it was something everyone used very frequently, didn’t know it was an ESSENTIAL FUNCTION.
You can read their comments about it here: We find that most of the time when we are splitting stuff
Anyway - right now you can only split stacks in half, RMB will do that for you. Good luck trying to separate exactly 25 items out of a stack of 1000.
They are brining back this essential function because of player backlash over its removal. Unfortunately it sounds like they are changing it from shift-drag to something else. I hope that I will be able to edit the .ini file to put it back to shift-drag because that’s what I’ve been used to for about 7 years… and it was PERFECTLY FINE THE WAY IT WAS, DENNIS!!!
Sorry about that. Had to get that out of my system… phew.