as I started the mess I will try to explain myself. It is mainly said above but I will but in my own words.
I'm mainly driven by the combination of the ideas / features
origin from the same background as stated in
mine too
The final wish is, to run Joplin headless combined with the Web application companion for Joplin on a server on my network (what is currently in reconstruction) allowing to share notes between family members and friends.
User accounts are provided by the sync target such as nextcloud.
A big surplus would be to have work and private profile with different settings (and notes by having a work and private account). You can imaging, profiles present roles and depending on your current role you need a different configuration,
First of all it needs to be answered what is stored in the profile, if it is anything (CSS style, preferences, search weighting, tags, sync-target, ...) but the notes than there is even some kind of user profile, as you switch sync-target, you may store at the same service using a different user account.
Of course, we are not going to introduce user account management but using multiple profiles is somehow a transition towards this although leaving the tough work, user management, to the sync-target.
I hope, I expressed it a bit more clearly this time.
I do have some thought about leaving the multiple profile to the OS of the app.
We want to keep Joplin app as simple as possible, so that any user can manage it. Setting up different user profiles on OS is still a tasks to more advanced users, in particular for Android and iOS.
So if we are going to have multiple profiles, like mother, father, kid (staying with the family idea), privacy could become an issue but depending on how GSoC Idea - Password-protected notes is implemented that could be solved
A last though, how could the web companion deal with multiple profiles?
It may need to spin-up another Joplin instance if two user open the web companion with their respective profiles, wouldn't it?
The question remaining is, how resource consuming is this approach, if operate with headless Joplin apps.
Last but not least, this does not happen at once but, if it is agreed to my thoughts, it shall keep the door open to continue development towards these features.