Delarations of Arduino.h not known

I've a strange behaviour in Arduino IDE 2. In a single sketch the function pinMode() (as well as OUTPUT, etc.) is not known to the programm and the related functionality does not work. The sketch may be compiled just fine btw.

grafik

In another sketch with the exact same logic there is no problem with pinmode() as well as with the related functionality. These things are declared in Arduino.h. Usually this file is included implicitly. Would it help to include Arduino.h explicitly and how would I have to do this?

@florian_k1, your topic has been moved to a more suitable location on the forum.

I think that in the section where I have moved your topic are a few more posts about it. The red squirly line is definitely known as a 'bug'.

Yes. In fact OUTPUT is not known as well.

@sterretje You're right. Seems like the error reported in the IDE is a false positive and the functionality is not working cause of a conflict with the SoftwareSerial library I'm using in the sketch for communication as well.