well I was thinking about "idle" icon in ASC - I tried but fail
here is my version of "idle engi mod"
1. show overlay for engi and for idle engi (off by default)
2. show overlay only for idle engi (on by default)
all so there are overlays for idle factory,SCU and ACU (off by default)
T1 engi is "1", T2 engi is "2",...
but switch is in file in modelus/engineers (scroll down) - you can check it
in vault is old version