of course, it can be done. go to ASR, find preset "Example: Set tag", either modify it or better copy it and modify the copy: set <tag 1> to your 'New tag', set <custom text 1> to 'Some value', tick 'assign hotkey for this preset' checkbox (DO NOT TICK preset for AUTO APPLYING!), click 'save all & close', and restart mb. after mb restart go to prefs> hotkeys: "Tagging Tools: (magnifying glass): Example: Set tag". assign hotkey to it.
it's somewhat inconvenient and not obvious to assign hotkeys to ASR presets, but it's limitation of mb api
p.s. sorry for late answer, i don't know why, but several last days haven't been visiting plugin's board.