I support that fully ++++I think it might be better to check if there is a \t in the string when appending the hotkey.
So if the \t is missing, append it and then the hotkey, otherwise just append the hotkey. This way, custom languages can define static hotkey labels and definitions like the Extended Menu could work without any changes.

To be precise there is not actually multiple \t's in the language file, but a conflict with \t's in the language file and hardcoded \t's.Multiple \t for a menu entry in a language file can be considered as erroneous and the language file should be fixed.
IMHO hardcoded shortcuts (hence \t's) should not exist in translatable menus - because then they are not really translatable

Take for example the German 5915="D&rucken...", 5921="Als Text &kopieren" and 5924="&Alles markieren" - they have Ctrl+P, Ctrl+C and Ctrl+A as shortcuts in the Lister menu (when using wcmd_deu.lng), where it should have been Strg+P, Strg+C and Strg+A


So as a workaround until these menus items are truely translatable including the shortcut,s and the translations are added to all .lng files - I think that implementing your suggestion would be the right thing to do.
Or in case of an \t in the language file - TC should simply not add the hardcoded shortcut - it is then up to the translator to include the formerly hardcoded shurtcut into the translation - for example change:
5912="&Next File\tAlt+Right / "
to:
5912="&Next File\tAlt+Right / N"
It would also make it possible to fix the Ctrl/Strg problem mentioned above.