It happens that you have to add several ISRC numbers to your tracks.
Some distributors create new ISRC numbers or new numbers appear in sale reports, which you have to enter in your system.
With Affekt Audio Management it is easy to add new ISRC numbers. Either select new numbers from your own root or manually insert the new number.
You can also delete numbers. Just keep in mind that the assignment might then be missing in a royalty calculation.