First of all: QMC2 is not MAMEUI. Apart from that, the favorites management is something you'd find on the TODO list as "planned for improvements". When it's done, it'll be done for all emulator targets.
Regarding software list favorites in qmc2.ini... there are good reasons they are "buried in qmc2.ini". Mainly because there are relations to the device- & slot-setup you can use with them. But I should allow exporting/importing them.