It would be really useful for me if, when working in a project, the open dialog for files would return to the root of the project folder if it’s travelled outside of it recently.

It’s only rarely, that when working in a project will I need to go outside of the project folders, so it’s a right pain to navigate to my project folder again through the dialog, since I find the project sidebar a bit clunky at times.

The open dialog starts in the directory of the active view’s file. Switch to a file in your project and it should work.