I think it would be useful to add the ability to hide the toolbar for certain components specifically iframe_panel similar to how ha-floorplan gives the option. This would allow for a cleaner look on the UI especially when the url of the iframe has its own toolbar.
ha-floorplan html file: This file uses hide_app_toolbar from it’s yaml configuration to hide the toolbar.
ha-panel-iframe.html file: This is the file I would assume needs to be updated but I am not familiar with polymer.