RE: Filter a View based on Sub-grid/Related Data
Hi SarahC,
In this scenario, an Opportunity can be associated with multiple Accounts, and an Account can also be associated with multiple Opportunities.
So, the relationship between Account and Opportunity is N:N.
In this case, we only need to add a sub-grid for both Account form and Opportunity form.
Step 1. new a N:N relationship for Account and Opportunity.

Step 2. Insert a sub-grid of this N:N relationship on the Account form and Opportunity form.


Test:
In the Opportunity "opp1", there are two related Account "acc1" and "acc2".

In the Opportunity "opp2", there are two related Account "acc2" and "acc3".

In the Account "acc1", there is a related Opportunity "opp1".

In the Account "acc2", there is two related Opportunity "opp1" and "opp2".

In the Account "acc3", there is a related Opportunity "opp2".
