To add such system properties, use Tools > Advanced options menu and add them as a comma separated list in the system property list box as seen below: (note property names must be entered in full and are case sensitive)
Once you click OK button and restart xplorer² ultimate, these properties are available for use everywhere in the program. So you can use View > Select columns menu to add them as extra folder details (see how we filtered the available columns list for audio in the screenshot below), to see the number of channels and sampling frequency of your MP3 files.
Likewise you can use such properties seamlessly to define search or filter rules, e.g. do a search for all music files that only have 1 channel (mono), or are sampled in lower 22050 Hz quality.
If you bought xplorer² professional and want to upgrade to ultimate edition, you can do so paying the difference in price, as long as you bought within the last year.