Nothing seems to happen when I select F6
Keep in mind the GSX editor doesn't really use the keyboard. It ask the sim through Simconnect to momentarily let it intercept EVENTS, which might be associated to a key or not. And in all the keys used while editing something, are the ones associated to the SLEW mode,
In case of F6, by default, the key is associated to the Slew Freeze Pitch command so, the first thing to check if F6 is STILL assigned to it, by going into Options->Controls, then select "SLEW" in the "Flight Mode" drop-down list, and use the Search box to find "freeze", you'll see some results, check if Slew (freeze pitch) is assigned to F6, which is the default.
Or, you can Search for F6, and see if it has been assigned to something else. To work with the GSX editor, it must be assigned to the Slew (freeze pitch) Event. Note that, you are not "forced" to use F6, you can assign anything you like, even some joystick button, as long is assigned to the Slew (freeze pitch) Event, GSX will use it to do what F6 would do by default. Just be careful, of course, not to create conflicts.
