[x]):The text about which branch should be merged into which other branch doesn't contain the name of the repository. In the screenshot below, it has the form organisation/branch
In my opinion the current behaviour is not really intuitive, it should either have the form org or user/repo:branch or just repo:branch.

if it's changed go for owner/repo:branch. Since if you go for repo:branch you don't know which fork it's coming from :)
I think best would be something like that: ... from fork_owner/repo:branch into devel
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I think best would be something like that:
... from fork_owner/repo:branch into devel