If you're playing on a windows machine, Autohotkey is probably the easiest solution. You can do key remapping based on the window that's open with #IfWinActive / #IfWinExist.
Writing the scripts is ugly, but effective and not too tough
I have to second AHK. Cube World was unplayable for me until I discovered it.
I've yet to find a reasonably good Linux clone of AHK, but then, most Linux games I've encountered tend to be quite configurable. Starbound comes to mind as problematic, but I haven't touched it in a few months.
Try using xbindkeys and xdotool together. xbindkeys uses guile as an extension language, with guile functions bound to keyboard shortcuts to invoke xdotool to simulate inputs. It works well enough that I get annoyed every time I have to deal with AHK's weird scripting language.
Writing the scripts is ugly, but effective and not too tough