If variable exists?

#1 -- If my variable (myvar) exists I want to use it in e.g the "Display Text Briefly" action

#2 -- If myvar does not exist I want to NOT use it. e.g. branch around the "Display Text Briefly" action mentioned in #1. Or simply display myvar as a blank.

Can this be done in KM?

To answer my own question:

Use the IF/THEN/ELSE action. If myvar "does not exist" then.........