How to reproduce: So on the left side there are the buttons: "Projects", "Documents", "Filesystem" and "Classes". I've Projects opened at the moment and want to open "Filesystem" under it. For that I click Ctrl+left on button "Filesystem" Actual behavior KDevelop opens it normally and replaces the previously opened "Projects" tab. Expected behavior: Both "Projects" & "Filesystem" visible. Note: This works fine in 5.0 branch, I think some of Anton's latest changes in sublime/ are related.
Note: From https://www.reddit.com/r/kde/comments/5nb4ro/kate_users_why_dont_you_try_kdevelop/dcacxpa/