Idea from discord, originally in the form of "reload a pack of cigarettes to reduce clutter".
A container reload function could list all the nearby items that can be put in it. For an already loaded item, it could just try to grab all the loose ones, then require another prompt to reload it with contents of other containers. Alternatively, it would always print a menu asking how it wants to collect the items.

Example uses:

• Reload a pack of cigarettes to repack all cigarettes into this pack, preferring to empty packs rather than to skim near-full ones
• Reload a lamp oil tank to siphon nearby bottles
• Reload a sack to fill it with flour (mostly RP reasons, as itemized flour is perfect usable)

Not sure if it's a good idea, because it sounds like it's just a different way of having a "collect all items of type" action.
Still, may be worth it, even if it's not perfect. Better is an enemy of good etc.