Transfer of multimedia files

Hello,

I use Calibre for eBooks and multimedia (e.g. mp4, mp3, webm) files.
I use Android devices (tablet, smartphone) as a playback device. However, I cannot transfer the multimedia files to the device using the "Transfer" functionality. The message appears that no suitable format was found.
As a workaround, I export the files to a directory using "drag and drop". However, this way I have no overview of the transferred files in Calibre.

I already asked a question along these lines some time ago: https://www.mobileread.com/forums/sh....php?p=4274858

However, I had difficulties implementing the suggestion described there with the source files.

I would therefore like to ask again whether there is an easier way.
Could this problem be solved with a small plugin?

Many thanks in advance and best regards, Steve