Firefox

If you have just recently received an update to Firefox on Android, you may find that all of your bookmarks now have sorting enabled with no option to turn it off.

There is a way (at the time of this post) to turn off this function.

Instructions for disabling automatic sorting currently:

1. Open settings.
2. Tap on About Firefox
3. Tap on the Firefox logo 5 times to enable developer settings.
4. Back out to the main settings menu, scroll down to Secret Settings, and tap on that.
5. Find the 'Enable Compose Bookmarks' toggle and turn it off.

It looks like it's something the Firefox dev's have decided that everyone needs this without any other alternatives.

https://connect.mozilla.org/t5/ideas/restore-ability-to-preserve-desktop-bookmark-order-in-firefox/idi-p/83114