A new UI feature is the ability to float or dock the Catalog Item Selector, this presents the items in the active catalog ready for activation with a single click.
Select a Building placement tool, say Wall.
In the placement dialog, click on the Catalog Item Selector then click on the pin icon to float the Catalog Item Selector.
It can then be left floating or docked in your preferred location. It can be docked in a tabbed stack like most other dockable dialogs.
Once the Catalog Item Selector is floating or docked note that the selector panel in the placement dialog loses its interactivity, the selection arrow is no longer displayed.
When a placement tool is not active the floating/docked Catalog Item Selector will be blank. When a placement tool is active it will populate with the content for that tool.