Related contacts of Account in Task - Lookup filter

Question

I have contact lookup in task. If I choose contact then it should show only related contacts to Account. I put the filter condition as follows

Activity: Related To ID equals Contact: Account ID

The above condition works fine if I create task from Account related list as Related To ID matches the Account Id whereas if I try to create task from Opportunity related list its not showing any contact as Related To ID in this case is Opportunity Id not Account Id.

I need to get Contact of parent Account as well for that I use the below condition

Activity: Related To ID equals Contact: Account:Parent Account ID

Is that possible to get the Contact of parent Account if so how to get that?

Answer 1

Since Contacts are not related to Opportunity that's why no Contact is displaying if you have that look up filter.

You should change the look up filter like this upon introducing the Id check for Account (001) and Opportunity (006).

Outcome:

1. Create Task from Account - it will filter all the contacts related to Account

2. Create Task from Opportunity - it will display all the contacts (25 records per page) as no filter is applicable here.

Update

Based on revised question if you want to include Grant Parent Account then it will be like this where contacts related to either of Parent Account or Grant Parent account will get filtered.

If you select Grant Parent Account then contacts both Grant Parent and Parents will get displayed.

If you select Parent Account then contacts of only Parent Account will get displayed. This time, contacts of Grant Parent will not be displayed.

(I have assumed then user has access to all the Account Levels).