Although I like the idea to have all info centralized I am afraid there are some complications.
To start with the last one:
import/export or somthing like Flow sharing is announced by Athom but not jet possible. So we have to wait on that.
You are free to create your Tutorial here on the Form, very welcome !! I hope we can use a category for Flow examples son here (We (some Moderators and Athom) are working on it already)
With the possible connected devices for Homey this would be a HUGE amount of work, probably always out-dated. I prefer to search at the manufacture sites to get up to date and (most) correct info.
For the Apps is is somewhat else, please be free to make for alle apps you create a Forum thread like we have done for some already or ask the Developer to do. and update the App in the store with a link to the Forum thread here.
and your first one:
For the Homey App most simple errors where pretty explanatory (to me), but others I have seen varying from code faults to authentication errors where full screens of java or JSON codes. I don’t see an easy way to organize that in a table or sheet here.
maybe someone will add and maintain a Topic here with errors but I am afraid the effort will not wight to the search on Google and ask a question on Slack or here when it happens.