Hi all, I'm re-submitted below question with a slight change in scenario.
We require to add a new sub-grid to leads form with following fields.
- Designation (lookup field)
- Response field (Text field)
I've managed to customize up to a certain level but it's not completely solved yet.
- I created a new entity along with required fields. Then created relationship between two entities.


- Then, I've added a sub-grid to main form of lead and assigned Active lead responses view
Note - It doesn't allow display new entity under 'Only related records'. Therefore had to select 'All record types' and pick the view


- After publishing all customization and when I attempt to add a lead response, it doesn't display any controller (text box/drop-down list) to enter data.

If someone can guide me to figure out this confusion, that'd be really appreciated.