Legitimate need for Child DocType within Child DocType

[revant_one]

@Chude_Osiegbu

conscious design decision

Table inside a table?

Adding tables in table is usually a bad design. Whats your use case?

You can have relation like

Project (istable=0), Project Task (istable=1) and Task(istable=0) :
Tasks are shown in Project as Child, Task are doctype on their own.

or Customer(istable=0), Contact(istable=0) and Address(istable=0)
Addresses and Contacts are rendered in html under Customer / Supplier.