Actually I should've called InsertMissingDefinitions. My bad.
If you have to insert a new quality you will want it inserted in the proper 'Weight' order. For example if you decide to split 'HDTV-480p' from SDTV you would give it weight 2 and increment WEBDL480p and everything higher.
Otherwise you would have to handle new additions via a database migration. This way you can simply add the Quality, update the DefaultQualityDefinitions table and let it roll.
Please note that QualityId is hardcoded, nothing is going to change that, and Id only resides in the db.