There was this idea years ago and it wasn't implemented at the time.
It's time to implement this Spotify!
Today we have the Family and Duo plans and more people are using the same device to listen to music. I personally want to switch to the duo plan with my fiancé but didn't make the change yet because we mostly use our PC as a media center and use Spotify on it more than on mobile. It would be great if we can both still use the media center and not just use the profile of one of us and miss up the music preferences.
This feature should only be on desktop clients and smart TVs and such. On mobile it makes less sense.
Updated on 2020-09-24
As you mentioned, a similar Idea has also been suggested, and only one thread can exist per idea:
If possible, vote for it, and add a comment there, so it may be considered. Any update on the matter should be posted there.
For more info on how the Ideas Board works, click here. 🙂