Timo, I'm not a dev either. What I've heard/read about the delay is that it's checking to see if ingrediants are in player inventory to craft the recipes in the selected list.
Seems the reason it does that is so it can list craftable (all ingrediants avail) recipes at the top of the list, even, or I guess especially, when that list may be 10 pages long.
This is also, apparently, the culprit as to why crafting speed is itself effected. Each time an item is crafted, while the crafting window is open, the player inventory changes, so the 'list' is re-parsed against ingrediants.
Just how I understand it. May be totally off base, if so hopefully someone will correct me.
Edit: (lightbulb) no idea if possible but _could_ the 'check for ingrediants>sort list' loop be turned off?
I for one would happily disable that auto check/sort if it meant no menu delays...