I also found this AppleScript here in the Forum (Link) from @Max_Megalon, but this code worked just once here (and opened AppleMusic instead), I restarted BTT but it never run again. 
for a german system use : "Kontrollzentrum"
tell application "System Events"
tell its application process "Kontrollzentrum"
tell its menu bar 1
-- click on and open Control Center drop down
tell (UI elements whose description is "Kontrollzentrum")
click
end tell
end tell
-- interact with Control Center window
tell its window "Kontrollzentrum"
delay 0.5
-- click screen mirroring button
set screenMirroringButton to button 2 of group 1
-- click screenMirroringButton click doesn't work
perform action 1 of screenMirroringButton
delay 0.5
set myScreen to checkbox 1 of its scroll area 1 of group 1
perform action 1 of myScreen
end tell
end tell
end tell