In my project properties I selected C/C++ General -> Formatter and checked Enable project specific settings.
Then I selected one of the built-in and went to edit and saved with new name and selected that.
Source->Format however still sticks to the formatter that I based my custom one on instead of my formatter.
The formatter I used as base is the BSD/Allman one.
It also doesn’t matter if I use project specific or workspace wide configuration.