As above, in Windows 10 version 1803, , the control panel shortcut now just brings up Settings.
But the following worked:
Right-click on the file, select "Open With" and click "Choose another app" at the bottom of the right-click menu.
Clicking that gives the dialog box with default app selection that ends with "Look for an app in the Store".
Here's the tricky bit: Click on the white space under the last option. This extends the list!
Scroll to the bottom of this list (assuming your app isn't listed).
Click on the white space, under the last option, again!
You should be taken to the Windows standard File Open dialog, where you can browse to your program of choice. (Worked for me.)
1You are comparing the UWP method of setting the default application to the legacy method. Legacy method is still accessible through control panel – Ramhound – 2017-11-29T23:31:28.120
4@ramhound not in the newest version of Windows 10. Microsoft continues to deprecate those legacy control panel functions and redirects to the newer version, which for some reason all seem to be extremely limited in functionality. I’m with the OP, I was a bit pissed off about this one. – Appleoddity – 2017-11-29T23:59:05.367