I don’t have Qlab or anything like it, the StageCaller homepage says you can trigger the app with preinstalled software or free software but the instructions don’t say what or how?!
well - qlab would be easiest since that’s pretty much industry standard - you could use a program called ‘MidiKeys’ to send simple MIDI commands… and there are numerous OSC things out there
I guess the first question is what are you trying to do…