Gitlab add project to existing milestone

Question

I want to use gitlab group breakpoints.

When adding a new milestone, you can add several projects. When the creation is completed and saved, then you cannot add the project.

Answer 1

I added a milestone with exactly the same name and date and it is automatically assigned to the correct group value. They do not even have the same identifiers in their respective repositories. So it seems that they just have to be equal and not the same ...