Creation of this task was suggested by @Jdforrester-WMF on the wikitech-l .
The goal is to discuss how extension developers can bind on (public) events in VisualEditor to alter its behavior.
As an example, this is the case from the mailing list:
I want to check if a category is set and if it is not, show a message window to the user before he/she can save. I've already implemented a serverside check and the API returns an error if no category is set. But this API error message cannot be styled/customized and it gets displayed after the user clicked "save".
This would need some kind of "pre-save" hook that one can bind to. James told me that there are some plans for such a system. Maybe we can share thoughts about it here.