UI Dashboard Theme issues

I am running Node Red from my Victron Venus server contained in Cerbo so I am not sure if my findings are relatet to this tspecic of installation or not.
I changed my Dashboard theme to "Dark Mode" and subsequently to "custom" but when I returned to the dashboard, I found that one of the groups, in fact the first one, had migrated to a different Tab.
Is this to be expected or just a one off?
Thaks