If you want to change the name of a specific video file you do it like with any other file, open for example the Files app>go to the file you want to change name>long press on it>top right 3 dots menu>Change name.
If you want to change the name of a specific video file you do it like with any other file, open for example the Files app>go to the file you want to change name>long press on it>top right 3 dots menu>Change name.
