Cannot find backlog in jira-software source


i’m working on some small improvements for jira bundled in a plugin. For example I want to extend the issue context menu in a scrum-project backlog, so one can move an issue to the top of a long sprint without having to drag & drop and scroll multiple times, but by a simple right click.

The documentation gives no hint about a matching location that one could simply extend, so i decided to have a look into jira sources. But when i search the code for strings like “backlog”, “scrum” or “sprint” i only find some test resources or conditional import references. I understand that “Jira Software” is technically a plugin and not part of jira-core. But it seems like it is not contained in the sources at all? Do i need to download other sources, too? If so, where can i find them?

As i need to develop some other tools later, a hint about that would be really helpful.

Thanks in advance for any (try to) help!