It's not entirely clear what you want to do. There is a toolbar with the port and monitor options on it called Micro Communications. By default the toolbar visibility is set to "automatic" which means that the toolbar will only appear when an arduino sketch is open.

You can control the automatic visibility using the vMicro>Tool bar Visibility menu item. if you switch it off you can then right click te VS tool stip and hide/show the Visual Micro bars just like any other Visual Studio bar.

With the tool bar visbility you have a shortcut button to the port monitor. 

If you are asking about how to customize the silly Visual Studio Start Screen that appears in VS2019, you can not. I suggest you switch it off in the Tools>Options. The Start screen gives nothing than is not also available on the standard IDE tools bars and menus! The Start Screen was designed by people who think the entire world want to do nothing more than open or create a project. You might get the idea that I do not like it

Other: You can also set the port monitor to open automatically after each upload and you can use the standard Visual Studio Custmization menus to add any Visual Micro button or menu as to any other toolbar or menu.