What Does a Filter Do?
A filter can be used to ensure that a field with a specific value will or will not be populated through the Formstack Sync.
How Do I Add a Filter?
When you are building your mappings, within each field mapping you will see a tab labeled Filters. This is a feature that is closely related to the Workflow application (learn more about Workflows). However, unlike Workflows that lets you control the actions of an entire record (i.e. contact, company, etc.), the mapping filter just focuses on the specific field you are mapping.
Lets take the above screenshot example of the Company Name field in Zoho on the Lead object. Under the Filters tab, we are going to add a rule for the Zoho Lead object where this field (Company) does not contain ACME CORP. For this example, ACME corp is a generic Company that we use, as a default, when we aren't sure what company a lead is associated with. We don't want to sync these records to HubSpot because we'd rather the Contacts remain independent of ACME Corp until we know for sure that is the company they belong to.
So what will happen is if a particular record passes one of your main Workflow rules and is therefore allowed to sync across to the other system? If the company name is ACME Corp then that field will be blank in the other system. However, if the company name is something other than ACME Corp, then the company name field will be filled in.
While the "IF" statement has both an Any and All option just like the Workflow logic, the mapping conditions can only support Any at this time. This is because you need to both have a rule that represents both systems where you are syncing the field. You only need to restrict the filter on the side where you want to limit when this mapping can be executed (i.e. in above example we only restrict the Zoho field but not the HubSpot field).