I have to spend some time on this. The whole Stellarmate app is something I just don't use. I use the noVNC Connect for everything.
Maybe I'm missing some ease of use because the screens seem much simpler and easier to use on a tablet/phone.
One quick comment. The manual was very helpful getting a newbie up and running. There have been a couple of walls, but the biggest was getting the camera cards unmounted. They need to be there for file backup on the Nikon as far as I can tell, but they mounted on startup, and none of the preference settings on the Pi (StellarMate AG) include not mounting drives on startup. Using the manual I was led to the DSLR FAQ, which led to a post in the INDI forum to use terminal to add this command:
gsettings set org.gnome.desktop.media-handling automount false
This solved my startup and control issue for the Nikon D5. You may want to add this.