I keep radio IDs in a spreadsheet and then when I program a radio, I add the radio IDs associated with a given system as radio IDs on that system only.
Keep in mind that radio IDs are not universally unique. This isn't a huge problem for large public safety systems - particularly if you are stationary. However, if does become a problem if you are mobile and/or listening to smaller systems (think business, DMR, NXDN, etc.) that use the same IDs within each/their system(s).
Not a Radio Shack fan.....