In the Mac OS there is an option to minimize windows into an app's Dock icon instead of into a separate icon on the end of the Dock:
It is a great way to reduce clutter in Docks that have lots of items in them.
The problem with using it in the Mac Affinity apps is quite a few windows (among them Typography, Guides, & the 4 Managers on the View menu) each include a Mac-standard yellow 'minimize window' button in the window title bar. So while clicking that button (or double-clicking on the titlebar) does minimize those windows into the app's Dock icon, there does not seem to be any way to get them back out other than quitting & restarting the Affinity app.