I've been experimenting with ways to cross-link menus between flask applications running on different ports on the same server. None of the obvious ways to link to, say, the piHole menu on port :9012 from the Blinkter root page on port :9013 work. The best solution I could find via Google was a suggestion by Craig McQueen on StackExchange. When the link is clicked (onclick), a little embedded javascript is run to add the port number to the link. I've modified Craig's approach slightly to run the same script on right-click (oncontextmenu). This is to allow <right-click>, <open in new tab>, or <copy link location>.

<h5>
<a href="/" onclick="javascript:event.target.port=9010" oncontextmenu="javascript:event.target.port=9010">SysInfo</a>
  •  
<a href="/" onclick="javascript:event.target.port=9011" oncontextmenu="javascript:event.target.port=9011">VoiceBox</a>
  •  
<a href="/" onclick="javascript:event.target.port=9012" oncontextmenu="javascript:event.target.port=9012">piHole</a>
  •  
<a href="/" onclick="javascript:event.target.port=9013" oncontextmenu="javascript:event.target.port=9013">Blinkter</a>
</h5>

And the end result looks like this:

I'm going to add this menu bar to the bottom of the root pages of each of the server programs. Hacky, but good enough for my needs.