There are some possibilities, although this may not be exactly what you think.
You can transfer resources using a ResourceDictionary. This is very convenient for styles and templates. Of course, you should organize your XAML in such a way that you can use it (for example, using ControlTemplates).
Alternatively, you can create UserControls that encapsulate parts of your XAML. It depends on your layout.
, , XAML xmlns:??? .