Loop over multiple A-B points in mpv.
Place multiloop.lua in your scripts folder, generally ~/.config/mpv/scripts/ (GNU/Linux) or %AppData%\mpv\scripts\ (Windows), or start mpv with --scripts=/path/to/multiloop.lua.
The script is activated by the M (shift+m) key. This can be changed by editing the keybind variable at the beginning of the file.
Follow the on-screen instructions. If you decide to save the A-B points for future use, a file with the same name as the file you are playing and "mab" extension will be created. The points will be restored from this file when activating the script.
Once looping, to exit you'll have to quit mpv.