Add Source to Activity Timeline advanced filters

We have emails syncing from Salesforce automatically as well as those that are logged by the CSM through GS Assist on the Timeline. Would like the option to filter out Salesforce synced activities and only look at the ones manually logged by CSMs but are unable to do so as the Source field is missing from Advanced filters on Activity Timeline. It would be nice to have parity with the field as we’re able to use it in Rules Engine.

Source not available in Timeline Advanced filtering:

But Source is available in Rules Engine