I confess that this is probably a pretty basic workflow question, but in testing Collaborations with Word, Excel and PP I noticed that creating a new document or slideshow appears to work fine, but I cannot quite figure out how to collaborate using an existing document or slideshow. I don't see an option when setting it up to choose an existing file. Moreover, once in PowerPoint (or another Office app) and working on an existing document (File > Open) the only way to invite those same collaborators is through O365 Sharing. At that point Canvas sharing preferences no longer function. I'm wondering if the only way to work on an existing document or slideshow is for the owner to open said file and re-save it using the same file name used when the collaboration was created (?). I'll test that next.
Secondly, the file appears to 'live' on the faculty members' O365 account. (Or whomever initiates the collaboration.) I wonder if there is a way to transfer 'ownership' of the file to one of the collaborators (?). I suppose the file can be sent to another person, but I assume Canvas collaboration preferences would again be rendered useless and the document would need to be shared using standard O365 Sharing..