TL;DR
When holding an item and hovering over a building, pressing Z could insert one item (if it fits).What ?
Currently we have shortcuts for inserting half a stack (Ctrl+RMB) or a full stack (Ctrl+LMB), but inserting individual or few items requires opening the regular interface. Since there's already a command meaning "drop one", why not extend this to work with buildings?Alternatively, a new command (Ctrl+Shift+LMB or whatever) could be added to accomplish this.