Foobar2000:Backing up configuration
Hold shift, click "File" menu. Near the bottom, below "Preferences", a "Browse configuration folder" command will appear, click it. It will reveal the folder where foobar2000 configuration data resides.
In case of portable installs, it will obviously show the foobar2000 application folder.
To back up your foobar2000 configuration, first close foobar2000 and create a copy of the whole folder. You can later restore it at any time to undo any unwanted changes in your settings.
Backing settings up is good in particular before upgrading to a new major version, in case you want to revert without losing any settings.