X-T5 - Disable PROTECT with the AF-ON button?

[Berold]

Hello, My X-T5 uses the AF-ON button to protect images (little lock symbol) when in playback mode.

I accidentally press this a lot when shooting.

I'd like to disable this, but I can't find a way to change it. It's really annoying as I often accidentally protect random images and then I have to search them out and un-protect them later on my computer when I want to delete them.

I've looked at the custom buttons menu, but there doesn't seem to be an option for mapping these in playback mode, and the AF-ON button is just listed at AF-ON for back button focus, which I use.

TIA!