How to add an existing issue as a sub-issue of other existing issue

[klion26]

Hi, I'm using Huly to track issues. Thanks for this project.

currently, I found that I can't attach an existing issue as a sub-issue of another existing issue, I can only create a new sub-issue, I can't attach existing issues as a sub-issue of another one.

[haiodo]

Hi, right now it is available via context menu only, since it rare action.