Hi. There's a program called Clover Configurator that you can use to mount your EFI partition (there may be better ways to do this, but this is how I solved it...).
After you mount it, you will have the option to open the partition. When you do that, it should open a finder window showing your EFI folder. Open it. Your config.plist file should be in the clover folder.
The best way I found to make these simple edits was to use a text editor. Right-click on it and choose "open with - other" and select "all applications" and then choose TextEdit. Find <key>Boot</key> and you should see <key>Debug</key> right below. There should be an entry saying "true". Change that to "false". Save.
Sorry for the long winded explanation (and probably not the best), but I'm new at this too.
Cheers