I need to be able to open it separately to fill in the items on one hand.
On the other hand i’d like to use it as a child table for other doctype. All the existing items should be visible and the corresponding check-boxes should be editable from the parent doctype.
I did exactly what you suggest but the problem is that inside parent doc i can’t see the existing records in child, instead i can add new records but this is not what i need. The child table should be populated in a separate form and all these records should be visible in the form of parent doc and editable.