Loading multiple ISO via WebApp (retroarch)

[yhilg]

How does one get a multiple disk game loaded into the WebApp?

The closest I found was:
https://www.reddit.com/r/RetroArch/comments/tycnkz/so_how_do_i_play_games_with_multiple_discs_in/

But I understand .m3u is not an option here. Would I need to extract all ISO into 1 big folder and recreate ISO from that to reupload as new?