Is it possible to use the top menu for other things than tabs for different views? I would like to use it for entities like temp and other things. Is this possible?
Do you mean to have the reading of temps instead of buttons to switch views?
Yes exactly!
So, is this possible or not? 
I’m not sure but I think you cannot.
There is way though to do this in the sidebar, I have seen mods for the sidebar that make it more of a dashboard.
Maybe you can get some inspiration here: Help with some code to display time and date