Windows 10 no longer allows portable apps to be set as default?

Question

In earlier versions of Windows 10, I was able to set _any_app_ as the default app. e.g. For Firefox Portable or MediaMonkey Portable, I could do something like: go to Control Panel > Default apps and Right Click > Open With > Choose Default Program > Browse... and choose any app installed on the drive.

On my newly installed laptop (Windows 10 Build 17134), the only options shown for choosing alternative apps are: 1) apps that are already registered/installed b) other apps that are available via the App store

Anyone know of a way to set portable apps as the default apps in the latest version of Windows 10 ?

EDIT 10/28/2019: The question as phrased above is a bit unclear. I'm asking about how to associate portable Browser/Mail apps with protocols such as http://, https://, mailto://, etc.

Answer 1

So it turns out that in current versions of Windows 10, in order to associate a portable app with a protocol the portable app must first be registered to Windows. In firefox this can be done as follows:

1. Firefox > Tools > Options --> 'Make default...'.
2. In Windows, use 'Choose default program' to select Firefox as the default browser.

I found this answer at https://www.dslreports.com/forum/r31869188-Make-a-Firefox-portable-the-default-browser-RESOLVED

Answer 2

So simple, instead of including your desired app in the Default App's list, use firefox to do it for you. After clicking "Make Default"(in firefox options) automatically you will see the FF-Portable listed in your desired segment(in windows 10 Default Apps popUp window). Thanks to @RustyMonkey.