Startmenu page_id

since MUI 1.68 the startmenu pagemacro requires a page-id.
what's that?
how does it look like?
is there any default value, i could set?
and why is this ever needed?

i'm sorry ...

It's an id that you choose. It can be any string and it's only used on the compiler side. You should use the same string for every start menu page macro that you want to relate to the same page. It's there so you can have multiple start menu pages.