The excludes file has been discussed at some length under the Play menu, Section 2 ('Play music with defaults'). It is a simple text file that contains one composer name per line. If a composer is mentioned in this file, it means Giocoso has a 'hard ban' on playing anything composed by that composer. Entries can be deleted (or commented out) at any time, and then that composer's music immediately becomes playable once more.
The excludes file is stored as $HOME/.local/share/giocoso3/txt/excludes.txt. Since it is merely a text file, it can be edited in that folder using any text editor you like. The Administration menu Option 1 simply provides basic text editing capability from within Giocoso itself as something of a convenience. Taking it causes the file to be opened within whatever text editor happens to be configured as the default for your operating system: most Linux distros these days seem to use nano for that purpose, but you can configure any other text editor to be the default by the command export EDITOR=xxxx issued before launching Giocoso; a permanent change to the default editor can be effected by typing the same command into your $HOME/.bashrc file.
Whatever your default editor, when Administration menu Option 1 is taken, it will open the excludes.txt ready for you to make edits to it:
Each composer who you definitely and absolutely do not want to be played needs to be listed on a separate line, spelled exactly as you have tagged your music files. If you have, for example, tagged music with 'Wolfgang Mozart', then it's pointless to mention 'Wolfgang Amadeus Mozart' here: there won't be an exact match and any music that happens to have been composed by any member of the Mozart clan will be valid for random selection.
To remove a composer from the 'banned list', you could of course simply delete the line on which that composer's name appears in the excludes.txt. You can also merely comment out the name by sticking a '#' in front of it. Here, for example:
...whilst Wolfgang Amadeus Mozart is mentioned in the excludes.txt, his music is playable by Giocoso, because the hash symbol at the start of his name means he's no longer considered an active member of the excludes club.
When you've edited the file to your heart's content, use the standard file save tools to write the modified file back to disk. In nano, that means typing Ctrl+X and then tapping 'y' to confirm the save when prompted. Control is then passed back to the Administration menu. The next 'play' performed by Giocoso will automatically pick up any changes to the excludes file: you don't need to re-start Giocoso for that to happen.