You can create SPFx extensions with SharePoint Framework solutions, but currently not with add-ins. Could you be slightly more specific on what exactly you are looking and the reasoning behind of the ask, so that we can evaluate your input? Thanks for the additional details advance.
18 votesin the plans · 2 comments · SharePoint Dev Platform » SharePoint Framework · Flag idea as inappropriate… · Admin →
Thanks for the suggestion Wictor. I have added this to the backlog for review.
To clarify, is your suggestion that we have an admin UX to update the script and other resources locations in the app catalog?