Keep ToolWindow Open Even If Parent Controller Is Unloaded

Is there anyway to maintain a ToolWindow open indefinitely? I don't want the ToolWindow to close unless the user clicks the close button or dock button. 

In my case I have one (of many) active view at all times, like this:

<ContentControl Content="{Binding ActiveViewModel}"/>

When my ActiveViewModel == MyDockSiteViewModel, I display my docksite view where I can float my single ToolView. If my ToolView is floating I would like it to stay open even if my ActiveViewModel changes.

Is there any way to do this or would you recommend me to do this a different way?

I was thinking I capture the UserControl unload event and prevent my ToolWindow from closing or something.

See here:
https://i.imgur.com/L4f70Oi.png