Default portable applications in Windows 10

[JohnW]

Recently, my wife (who is not computer literate) wanted a program to view images with the ability to do some casual editing (lighting, colours etc).
Others may have their favourites; mine is Faststone Image Viewer.
I put the portable version on the computer and then found that it seems impossible to make it the default image viewer. The reason is that my wife runs Windows 10. I run Windows 7 on my PC so lack detailed knowhow on Win10.
I am very surprised that this issue has not been discussed on this forum.
I have googled for solutions and it seems that there might be a way via the Control Panel to associate file types. A long procedure although most of the images are jpeg.
As an interesting aside, I came across a reference to the use of MPC-BE whereby there is an option inside the program to set as default very simply within Win10. If this is true then why MPC-BE and not others.
I am coming to the conclusion that I should used the installable version of FSViewer!
How have others on this forum solved the problem?
Or am I missing something?

[SYSTEM]

Windows 10 does not allow a program to set itself as default (because that capability was often abused).

Most likely is that MPC-BE's option to set itself as default doesn't work.

[webfork]

Windows 10 does not allow a program to set itself as default (because that capability was often abused).

Thanks. That explains a lot of issues I've had on Win10.