In ArcGIS Pro 3.0, a user can navigate to a Geoprocessing Toolbox by using the Catalog Pane.
It looks like:
Catalog > Toolboxes > Some_Custom_Toolbox > Some_Custom_Tool
And the tool is opened under the Geoprocessing Pane.
If the user then clicks the "Back" arrow in the Geoprocessing Pane, the GUI does not go back to the Catalog Pane. The GUI goes back to the previous state of the Geoprocessing Pane.
To me, this is unexpected and non-intuitive behavior. "Back" should always go back.