How can I add my custom doctype to this list?

I Created a new doctype called BuyerContract How can I find it this list?

Hello @mohamed_prosepra

If doctype is created properly then it will show in your link field.

Might be If your doctype is Child Table or Is Single type then it will not show.

Check is there any filter is applied on your link field ?

OR

You need to define “BuyerContract” doctype name in Option for link field.
See the below screenshot example for customer.

Thanks