Funnel now has a dimension called Funnel Account id, which will contain the id of the Funnel account your viewing or exporting data from. This is can be seen for example in the URL of the Funnel app, e.g. app.funnel.io/#/account/<your_account_id>/dataexplorer/.
This dimension can be useful in Data Warehouse Exports where you might be exporting data from multiple Funnel accounts into a single BigQuery table or S3 bucket. In this instance the Funnel account id dimension will allow you to tell which of your Funnel accounts the data belongs to from within your Data Warehouse.