It's very helpful at times to step through the Qt source code. Doing so requires downloading the source code and then mapping Qt Creator to the appropriate source folder. Example:

However, when I switch build kits (e.g., switching from 5.12.0 to 5.11.1), the source code still maps to whatever version it happened to be set to – in my case, it was still set to map to the 5.12.0 source code even though I switched to build with my 5.11.1.

This was jarring for me and resulted in a lot of wasted time while I debugged the wrong source code. It'd be nice if this sort of source mapping was a part of the Qt kits.