Customizable issue sidebar order

Problem to solve

It would be incredibly useful to reorder items in the sidebar according to what you use most often.

Proposal

It should be possible to reorder items in the issue sidebar (for example, it should be possible to move Time Tracking to the bottom of the sidebar).

Related links

• This issue was motivated by a comment in another issue: "maybe we could do some UX research on the issue sidebar. Maybe the order of items could be improved, or we could add some configuration options to hide things you don't use (for example I don't use time tracking, but it's right there near the top of the sidebar: https://gitlab.com/gitlab-org/gitlab-ce/issues/26131"