In “link” field type,
I need to force the users to create new docs without listing the previously created ones
I’m not quite sure but it’s worth checking the Role Permissions Manager for any permissions set for the link doctype.
also not quite sure about your use case… but you can apply a filter to the list, that will force the creation… have a look at e.g. How to restrict supplier field on Purchase Order screen to certain values based on filter - #5 by mayur_hotmail