Works! Thanks a lot!
To publish a state change on the sonoff basic (topic=SonoffT1) to the 3 channel touch (Topic=SonoffT4), I had to add a rule there as well.
at the touch:
rule1 ON POWER3#State DO Publish cmnd/SonoffT1/POWER %value% ENDON
at the basic
rule1 ON POWER1#State DO Publish cmnd/SonoffT4/POWER3 %value% ENDON
Thanks again an all the best
Marco