Custom fields to appear in Explore before they have data associated with them

"For a custom field to be accessible in Explore as an attribute, there first needs to be data associated with the field", taken from this article: I created a new custom field but it is missing in Explore – Zendesk help

I would like to pro-actively build dashboards for new custom fields on forms but as they don't appear in explore until they are used on tickets I cannot do this. Even fields that never get used are helpful to report on as I can then amend my forms to exclude fields that aren't selected over a longer period of time.