[Feature Request] Custom Menu bar

Hi this is a pretty straightforward request, I can be implemented by editing the editor but thought maybe it would be useful in a standard build too.

As you can see below my UI setup uses a lot of floating windows on the second monitor. I have a habit of closing/minimising them especially when swapping over to another application. The red area marked has a lot of space for extra buttons. There is already a “Show Content Browser” Button. It would be nice if you could place buttons from the window menu onto the toolbar. Also if they worked like sticky buttons, so if you click it, it remains pressed while the window is open and maximised, if it isnt visible then the button would switch to inactive so you can easily find windows while working.