This is already possible via issue linking feature: https://medium.com/p/6bbf94ec0547

Thank you, it wasn't obvious that it has to be configured separately.

I think I configured it correctly, didn't restrict the linking (default "all projects") yet it seems the linking is only available within single project? Would it be possible to enable inter-linking projects (that would be helpful with certain features affecting multiple projects/modules)?

When linking to other projects, type in project path first in the search box. For instance: myproject/child# then you can search issues in that project

OK, this works with a "but": when typing project structure there is no autocomplete (neither project name nor searching in the titles). I think that when configuring linking/association, there should be a toggle whether the linking (or rather yet "searching") should be limited to project or global, and with global the list would search issues within all projects.

After typing project path followed by #, you should be able to search issues in that project.

Hmm, it seems it works. I think I was putting space after # which broke it (I assume that immediately after # I should only put issue number).

Still, auto-fill of project names would be useful as well still.