The common trend for music licensing is that your music should be licensed in a non-exclusive manner. This means you can sell a license for the same song to multiple customers and on multiple platforms (as long as you don’t promise them exclusivity). Regardless, some publishers/composers do prefer to sell only exclusive licenses. This means that each song can be sold only once (exclusively). It’s a matter of preference, as well as some high-end customers might require an exclusive license (for a movie for example).
By default, LicenseQuote works as a non-exclusive storefront for your tracks but can also be used to sell exclusive licenses.
To do so, you can mention in your store’s description, License Types descriptions and Agreement text, that the licenses you sell are exclusive. See the Rate-Card editing section for more info on how to change those. Then, each time you sell an exclusive license, you will need to remove that track from LicenseQuote (and from any other place). You can’t delete the track as it is linked from the licensing agreement you just sold (and made available for the customer to download it), but you can hide it from the store so that no one else buys a license for the same track. You might also want to change the track’s name and add something like “_SOLD” to its name, to avoid future confusion.