Thank you. Will read in-depth later today albeit from skimming it, I am not 100% sure it covers my case.
Update:After enabling (and then disabling) theming in project options I am getting duplicate errors (did not get any errors before) about mainicon...
When inspecting the Lazarus generated directory:
x86_64-win64 ... It now contains both:
1)
originating from
myapp.dpr:
{$IFDEF myms_App_Whatever1}
{$R ./resources/whatever1.res}
{$ENDIF}
{$IFDEF myms_App_Whatever2}
{$R ./resources/whatever2.res}
{$ENDIF}
2)
and the following .res files generated by lazarus:
So... I will reread the link you posted. But under all circumstances, the problem appears clear. Lazarus enforces generating its own .res file