The simple solution would be to save the standard template under a different name and the custom layout under the standard name. This way everything works for the normal layout and a custom debug layout can be configured directly. So for me it works as I need it (use a custom layout, but be able to switch to standard).
But if I select a different layout in 10.2, the IDE remembers this selection when I restart it. (Tested with Delphi 10.2 Version 25.0.26309.314 with MMX and CnPack as well as with Delphi 10.2 Version 25.0.27659.1188 with both addons)