There is a new feature in development for MBS Plugin and you can see it 16.0pr6 (see announcement here). We add the possibility to search in all scripts in the script workspace and find things.
For this we add a new search button (magnifier glass) to the toolbar on macOS on the right:

As well as on Windows with a regular button:

We even got a fancy tooltip to explain the button.
When you click the button, we take a snapshot of the current scripts in the window. Then we open a search window and pass the scripts. This may take a few seconds (or a minute for huge databases). Once the snapshot is loaded in the search window, you can start searching:

As you see we show you results as you type and highlight the found text. We show the script name (optionally with group name), the line number and what step this is.
When you make changes to the script, the snapshots ages. You may decide at any time to close the search window and open a new one.
On the Mac we can actually control the Script Workspace. You can click on the search result and we find the script (by name) and open it on the given line. There is a little chance that you have two scripts with the same name and this won't pick the right one.

You can have multiple search windows open. All the script data is held only in memory and you can only search the scripts where FileMaker allows you to see the content, so no worries for security. In case you close the Script Workspace, we close the related search windows. Use SyntaxColoring.ScriptSearchButton.SetEnabled function to enable or disable this or the checkbox in the preferences dialog.
Please try the feature and please give us feedback. Anything it doesn't find?