feat: partition main canvas vertically (#6759)

Co-authored-by: Marcel Mraz <marcel.mraz@adacta-fintech.com>
Co-authored-by: dwelle <luzar.david@gmail.com>

src/tests/zindex.test.tsx

@@ -94,7 +94,7 @@ const populateElements = (
     ),
     ...appState,
     selectedElementIds,
-  });
+  } as AppState);
 
   return selectedElementIds;
 };