plist file for launchd - To set up the existing script (remove_old_plex_files.sh) to run once every day and empty the trash, you can use launchd. Here are the steps to create a launchd plist file and configure it to run the script daily:

com.user.remove_old_plex_files.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>Label</key>
    <string>com.user.remove_old_plex_files</string>
    <key>ProgramArguments</key>
    <array>
        <string>/usr/local/bin/remove_old_plex_files.sh</string>
    </array>
    <key>StartCalendarInterval</key>
    <dict>
        <key>Hour</key>
        <integer>1</integer>
        <key>Minute</key>
        <integer>0</integer>
    </dict>
    <key>StandardErrorPath</key>
    <string>/tmp/com.user.remove_old_plex_files.err</string>
    <key>StandardOutPath</key>
    <string>/tmp/com.user.remove_old_plex_files.out</string>
</dict>
</plist>