Allysum?

Lobularia marítima aka Alyssum maritimum, a not frost hardy short lived plant or annual in colder zones. I think one overwintered for me in a mild winter, and they do reseed, but are easy to pull.
Lovely stuff, I think,

good for pollinators

Well alright! Thanks for the info! I live in zone 7b so it should be alright. I planted purple one year and it never came up, this was probably in a wild flower packet. :)