It will be much convenient to allow users to bind shortcut to a button / function. Users will be able to trigger them more quickly when they need.
Note that, in Excel users can bind a shortcut to a VBA macro. That proves that binding shortcuts is a real need.
This request is also valid for Word Add-in (there is a suggestion: https://officespdev.uservoice.com/forums/224641-general/suggestions/6572900-add-keyboard-shortcut), PowerPoint Add-in...
Thank you for the feedback! We’ve added this to our backlog and we’ll keep you posted with status updates.
Office Extensibility Team