Just to make this clear for everyone interested in this. The Projector offers DMX connection via XLR connectors and cables. This is helpfull to integrate all the functionality to an already existing light controlling desk.
But beside that, the projector offers ArtNet over the usual ethernet connection, which should exist in most cases anyway for easier configuration.
This is as well the case for others brands 'bigger' projectors, like epson or panasonic. But most of them do not offer the classic DMX via XLR.
This workflow is hugely optimized and allows you to bring in audio from any source along with the stage image recording.. this allows you to even mix in multiple audio sources if you like (narration being one use case).
Though, for OBS on macOS, you have to go to the trouble of making an "Aggregate Device" to capture the system audio. See this link for instructions on how to do that.
A different approach would be to have only one projector actor in a 'secondary scene' which is always active in the background (activate scene actor), and send the video outputs from each scene to it with the broadcast and listening actors instead of separated projector actors.
Here the tutorial about activating scenes in the background and the broadcast / listener actors.
As an advice in general. If I finish a project, I always archive the installation file of the Isadora version, with the actual project, I coded with it. Just in case, I need to reactivate it and have issues with newer Izzi versions.
I even keep the older version for a while in parallel in the same computer. On macOS, this is simple, as you can easily rename the applications name (adding the versions # e.g.). And install the second version.
Note: the plugins folder is also easily openable from the Isadora Help menu. Just go to Help > Open Plugin Folder > Troikatronix Actor Plugins
This way you can install the plugins directly. On Windows each plugin is contained in a folder with a name ending in ".izzyplug" You only need to copy the folder to this location and restart Isadora. (the shortcut simply makes finding the plugins folder even easier) The default path for the Plugins is: C:\Program Files\Common Files\TroikaTronix\Isadora Plugins
for me this would be a real game-changer. Isadora is an awesome interactive real-time performance tool, but enabling an easier media output workflow would bring it into the world of content creation without losing any of its distinctive heritage from the worlds of dance and theatre.
OK I now have a user actor which shows a green indicator for the current scene, has a lit button for "go" and "prev", and intelligently checks how many scenes there are in your patch and gives you a lit button linked to a jump actor for each one. Thanks to everyone who helped, as ever, any new task completed in Isadora comes with lots of new understanding for future projects.
If anyone has this same controller and would find this patch useful; here's the user actor that does all the stuff.