I just published a new article just before Christmas and year end! This article will show you how to create your own add-on to display your appointments from multiple calendars into a pane of Outlook 2017.
You can read it from http://emoreau.com/Entries/Articles/2017/12/Creating-an-Add-In-for-Outlook-in-Net.aspx.
Outlook is a great tool, I love it. My life is in there! But there is one feature that used to be provided 10 years ago which is not available anymore. That feature is a possibility of showing appointments from multiple calendars into the Calendar pane. I have, surely like most of you, many email addresses provided by my clients, each mailbox having a distinct calendar. I know you can get a combined view in the calendar view but not in the Calendar pane which is sitting right next to your list of emails, always visible. I missed that feature a lot until I found some code (developed for an older version of Visual Studio and Outlook) which was not working so great for my needs.
Figure 1: Toggling on/off the main Calendar pane