How to concatenate strings in global section?

ElCaron:
I would like to build multiple c-strings for MQTT topics in the global section of my sketch. All start with a prefix which I want to configure at one place.
What is the best way to do that, since I cannot use strcat and that sort of stuff in the global section?

Maybe it would be simpler to print the strings in parts - something like

Serial.print(prefix);
Serial.println(bodyA);

and on another occasion

Serial.print(prefix);
Serial.println(bodyB);

...R