Hi Mike,
The browse documentation button on the Script tool window should open the documentation for the Script process, not for the particular script whose instance is being edited. Script is one of the two internal PixInsight processes (the other one is ProcessContainer). Unlike normal processes, which are implemented by installable modules, internal processes are implemented in the core application.
So there is a small bug here (actually, a lacking routine in the core application---thanks for remembering me that I have to write it), since the Browse Documentation button on these tools should open the Process Explorer window to show the typical (and infamous) "Documentation for Script/ProcessContainer does not exist" message, but not a bug related to any specific script.