Great question - I'm not sure why that isn't available, but I will pass your feedback along.
In the meantime, I think your best option would be to add yourself to the collections overview page instead and then you could display all of a shop's collections and allow your users to choose the ones they want to work with from there.
I would GREATLY appreciate it if I could use the bulk editing functions from within a collections page. Often times I already have the needed products grouped in a collection and I just want to add a tag to all of them or something and I can't inside of the collections page. Very frustrating. So I have to go back to the entire list of products and select them again and then do the bulk edit. This would be a very beneficial and time-saving feature!
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