Create Outlook 2019 Addon for Win 10 Desktop Application, not Outlook 360

In outlook 2019 Win 10 Desktop application there is a default button on the VIEW menu 'MESSAGE PREVIEW'. The standard options for the VIEW - MESSAGE PREVIEW menu I can select: OFF 1 Lines 2 Lines 3 Lines I'd like to be add to add an option 'New Msg Only'. The other options would still work but only on 'UNREAD' or 'NEW' messages when 'New MSG Only' is enabled. All READ messages would not have a preview when the 'New Msg Only' option is selected. The number of LINES for the preview should still work when NEW MSG ONLY is checked. OFF NEW MSG ONLY 1 Lines 2 Lines 3 Lines This Outlook addon should work for versions 2013, 2016, but must work for 2019. This functionality was available in Outlook 2010, for reference. The menus is 2010 were different than in 2019. I own the code with the completed project.