SaraLi F. if you are speaking to the Site Builder tool, unfortunately at this time it is not possible to nest components - which is what you would have to do to make application shells work with other components.
You would have to do this in Figma or Webflow.
For Webflow, you would just follow the markers to help indicate which shells work with which navbar or topbars.
For other components, you should be able to paste in basically any component into the main wrapper of the application UI component - you may need to remove the padding-global or container div's - I don't remember fully off the top of my head here. But in Webflow its totally possible to build out application UI using our components.
