I found this
Creating Run Configurations for Subprojects
To prevent Qt Creator from automatically creating run configurations for SUBDIRS projects, specify the following variable in the .pro file of the SUBDIRS project: CONFIG += qtc_runnable.
Qt Creator creates run configurations only for subprojects that also have CONFIG += qtc_runnable set in their .pro files.
However, after using the "big icon" adding CONFIG to both SUBDIR .pro and the project I want to run I still run the project selected by the icon.
How do I "clear" the "icon" selection to test the CONFIG?
ADDENDUM,
let me say this - it somebody can point me to "purpose of the LEFT big icons" documentation I am game. It appears to be a "cute GUI" afterthought / replacement for "F1" help. ( There seems to be some relations to plain "options"... )
I find it "interesting" how SUB_DIRS options are so scattered throughout Qt documentation. qmake docs covers how to setup sequence of its works , but one have to use "big icons" to find out how to actually select which SUB_DIRS project. to execute. There is something missing in philosophy of SUB_DIRS here.
And in the process discovering "dependencies" .... ( next project - how to verify that these options are actually working ...)
Personally - I would prefer all these "big icons " options to be part of the standard window style menu driven scheme.