Is it possible to a menu item to the VenusOS?
Or are these all fixed and part of the build?
I am hoping there is a way to easily create a dbus path that is linked to a menu item and that the status can be read.
A parameter under my serial battery driver for instance.
Yes. You can edit the relevant Qml file in /opt/victronenergy/gui/qml. Most of these files simply bind to dbus paths to display them, so it is easy enough.
Of course it will be gone after every firmware update. But you could make your driver’s installer apply a patch if you wanted…
Just be careful not to break the Qml. If you do that, the gui starts with a blank white page and you’re kinda screwed if you don’t have ssh access…
Edit: On the topic of ssh access. Delete the file /service/openssh/down. This causes ssh to always come up. If you don’t do that, then the gui starts the ssh service (if so configured) and a broken gui can leave you locked out.
If you locked yourself out in such a manner, you can make a n sd-card with a venus-data.tar.gz file that installs an rc.local file which in turn deletes the down file. Just boot with that sd-card in the slot, and ssh becomes alive…
I guess I’m reading QML tutorials this weekend 
Thanks for the info. That is what I needed.