Sorry just to be clear - I really like GitLab - and I feel GitLab tries hard to make a great product for their users - and clearly they have a good understanding of the development community. It's just that I felt this issue had already been discussed and resolved - to be yet again undone. So just feeling frustrated we have to go through this again.
When you removed the sidebar last time - users of GitLab lobbied you hard to get that pin in there so they could keep that sidebar open at all times.
These kind of changes make me feel like you're not understanding (respecting) your customers' needs (desires).