On Custom Records, the sublist for the child record is uneditable on the line level by default. Follow the steps below to implement a Custom Record with an editable sublist for its child record.
Create Custom Record Type – A which serves as the Parent:
For more information, see article 10140 – Creating Custom Record Types
Make sure these checkboxes are checked:
Include Name Field
Allow Child Record Editing
Allow Delete
Create a Subtab on Custom Record Type – A:
Navigate to Customization > List, Records, & Fields > Record Types
Click Edit beside Custom Record Type – A
Click Subtabs
Title: Enter Custom Subtab
Click Save
Create Custom Record Type – B which serves as the Child:
Make sure these checkboxes are checked:
Allow Inline Editing
Allow Delete
Allow Child Record Editing
Create Custom Field in Custom Record Type – B:
Navigate to Customization > List, Records, & Fields > Record Types
Click Edit beside Custom Record Type – B
Click Fields
Click New Field
Label: Enter Label
Example: Enter Record Link
Type: Select List/Record
List/Record: Select Custom Record Type – A
Record Is Parent: Enter Checkmark
Click Display
Parent Subtab: Select Custom Subtab
Click Save
Click Save