Normally when you press delete button it deletes a stack of whatever the mouse is on, but it's not working for refined storage. Somebody told me in order to delete stuff you have to do a whole lot of roundabout dumb stuff. it seems kind of counter productive to make a mod called "refined storage" and then unrefine and deoptimize it to the point where you can't even delete a stack of flint to make room without first building several contraptions and waiting for it to slowly funnel the flint out of the storage disk

Normally when you press delete button it deletes a stack of whatever the mouse is on

This is not a thing. Some mod is likely adding that.

This would also break balance for many packs so is probably not going to happen either way.