Is there a way to create a custom keyboard shortcut in OSX?
This may be a viable solution, you'll have to give it a try and see:


This answer uses Safari as the browser, change as needed.
The Service1  was named Collaborator Keystroke, change as wanted.
The keyboard shortcut assigned to the Service is ^`, change as wanted.


For the Automator Service1:

Use the image below for the settings.

ApplesScript code:

tell application "System Events" to keystroke "]" using command down




For System Preferences > Keyboard > Shortcuts > Services:



Note: Sometimes with an Automator Service1 and assigning a keyboard shortcut, you may first have to trigger it from the target App's Services menu one time. From then on the keyboard shortcut should work normally.

1 In macOS Mojave an Automator Service is called a Quick Action.