If you have any, the best thing to use is a two part epoxy like Araldite here in the UK.
It even takes colour well when using acrylic style paints (only need a tiny amount to colour)
I’ve used it for years for many repairs especially like the one you mentioned. You just mix it and run it into the crack with a toothpick, then carefully sand the excess when dry.
There’s many previous posts on here of how popular it is for repairs.