Hi,
I have a floor-plan based upon the config-template-card.
There are too many icons and I need to reduce 
Now I want to hide the icon of the smoke-detector as long as no smoke has been detected.
How can I do this? I know GIYF, but I don’t find any documentation or help for that.
General suggestion:
post a SHORT version of the problematic card with MINIMAL number of entities and w/o unrelated things if you are looking for a help.
If by “floor plan” you mean a stock Picture elements card - then conditional elements (see Docs for this card) can be used to hide/show an element conditionally (i.e. this is unrelated to config-template-card).
If you placed a whole Picture elements card inside config-template-card (CTC) due to some reasons - this is a BAD practice; use CTC for a particular element (check Docs for CTC).
All CTC-related questions better to discuss in the main thread. Also, check if you really need CTC to achieve your goals.