I have added multiple telescopes, eyepieces, a camera, a barlow and two focal reducers to the equipment list. Besides the (known) inability to remove them, another issue I run into is that when I select them for the FOV overlay, always the first telescope is selected. For example if it lists "None", A, B, and when I select B, it uses A for the overlay. If I then select the FOV for editing, it selects "None" in the telescope list.
It only seems to be an issue with the first dropdown, for the telescope selection.
This is on SkySafari 6.0.2 Pro on macOS 10.13.4.