controlling volume from second device

[11180020422]

Spotify Premium

Netherlands

I have Spotify Premium installed on my desktop computer (Windows 8.1) and can control the Desktop volume using my Samsung Android phone.

What I can't do, I can't control the volume when the source is my Samsung Tab A using that same Samsung Android smartphone (a Galaxy Note 9).

So, I readily see the volume control on my Note 9 when the Desktop is playing Spotify, I just can't find the volume control option on the Note 9 when my Samsung Tab A is playing Spotify. 

Am I overlooking something or is this simply not possible at the moment?