By "calling a combat macro" we might mean "calling a combat macro from another combat macro", which is impossible (KoL itself would have to have that functionality, and it doesn't).
You could, theoretically, break the css into parts, convert some parts in combat macros, call consult scripts without using macros, and call named native combat macros as such. That might cause some problems with how some actions are inserted by consult scripts, and would be ideologically unclean - the "proper" way is to submit everything as a single native macro, wo we are waiting for KoL to implement that (maybe, eventually).
but they all show up under the Skills dropdown on the combat bar thingy
that doesn't let you check your css's validity before starting the fight