The Firestore panel is too narrow.

I fixed this with custom css:

.firebase-database {
  max-width: 100% !important;
  padding: 0 !important;
}

.viewer-container{
  max-width: 100% !important; 
}

Please just make this the default. Yes it doesn't look as pretty, but the current ui is borderline unusable when viewing documents.

The collection list & the document id lists can stay narrow, just make the document view much bigger and fill the available space.