Combining 2 Mono to 1 Stereo

I used to be able to highlight two mono files and click open. They would be opened as a stereo file with the top on in the left channel and the bottom one in the right.

I can’t seem to get this to work now. Is it still possible to do

This is still possible, but this is governed by name rules. Left and Right files are recognized according to their name.
This rules are customizable in the preferences.