+1, please add this.
It’s very weird that when I have a file open in a new window, and I hit the command to show backlinks to this file, this opens in the sidebar of a different window (the main window), which has other files open.
By the way this has been requested in other threads, e.g. Sidebars can't be accessed on additional windows, Having the sidebars open in multiple windows, and probably others.