What is the Python method to "turn on" existing QGIS 3 toolbars, as you manually do when you right-click in the toolbar area and select the toolbar that you want to appear?
So depending on the toolbar that you want to show or hide, you can do the following: iface.databaseToolBar().show()
or iface.databaseToolBar().hide()
You can find the available toolbars in the API. Just do a search for “ToolBar()”