Xperience 13 select multiple pages on page type field

I don't think it currently exists for Page types, I do agree it would be a useful addition.

At my agency, we previously created a custom "multiple page selector" form control that opens up Kentico's page selector and then manually stores the selected pages NodeGuids as a semi-colon separated list. You could look at doing something similar yourself.

Depending on the scenario you could look at using a Path selector instead - point the field to a folder of pages.

Alternatively, you could look at using Page Relationships or this RelationshipsExtended module.

What do you want to achieve exactly? Why you cannot use UniSelector form control for this and configure it to select multiple pages? This is the documentation about the whole control. But in the page type you can use the already available Universal selector form control, configure it to use either cms.document page type for any page or use just the page type code name, or cms.document.

Yeah UniSelector is another good alternative, but the interface for it doesn't use the Kentico page selector. The page selector is great for content editors, you can to find the documents in the tree rather than just a dropdown or similar.

It would be good to have a form control which allows for multiple pages to be selected using the Kentico page selector - this is something we did in our custom form control. I might discuss potentially releasing our form control on the marketplace.