No problem, you cannot change anything in the capabilities offered by SmartThings.
If you create a custom capability you can place your own text but the button will be quite boring.
Maybe @nayelyz can suggest the engineering team to create a proper capability for the Identify feature, using a play tone feels like a hack. My two cents: have a command with a time attribute, like identify(time) so if time is not provided it uses a default and if it’s 0 it stops. Controlling the time would be useful for lights and switches that can blink the light and use it as notifications.