How to get append to work with loadfile

[advice2020]

I apologize because I am probably overlooking something.
I know of umpv which offers option to append files that are opened to playlist in the same instance of mpv.

I was wondering what the use of something like this command is used for?
mpv loadfile <filename> append

When I try this command it opens up mpv playing that filename, but if you run this same command again with a different filename while the first file is still playing, it just opens up a new instance of mpv and plays that file as well at the same time.
So two instances of mpv are running at the same time, it does not append the second file to a playlist (at the end of list) in the first instance of mpv.

Thank You

[guidocella]

Commands are run from input.conf, not from the CLI.

[mrfragger]

use it to a main directory. Set to recursive then your playlist is loaded with all media ready to search the playlist

d-o loadfile "~/Music/somedir" append #! [Playlist] > Load a directory (customize it)

another way I achieve the same thing is bookmark some media that's in ~/Music/somedir and it'll load the playlist also

both these ways avoid having to go to your file manager or having to save an m3u playlist that changes every so often