How to isolate large controls from the main xaml markup in wpf?

Question

WPF

There is a big "menu", and it messes up the readability of the markup (at least for me). It would be desirable to remove all big controls in a separate place.
I tried to remove it into the resource dictionary and connect it through styles, no matter what, but the commands do not work. I suspect because the library does not have access to the main xaml.
In general, the question is: what are the ways to do this?