this is the default functionality that can be achieved using some simple steps.

1. when you create a lookup field of account on object tracking.
2. then add a sub-grid on account (make sure to selected related records and entity only) and it will only show when the record is saved.
3. '+' button to add an object is available by default
4. when you add, the account will be populated by default.

you do not have to do any out of the box thing to achieve this functionality