How can one build an OKR Board Custom Dashboard to present Custom Field data?

[E. Manning]

We use the Custom Dashboard feature on the OKR Board to monitor progress on OKRs during a Quarter.

At present the data options for the Custom OKR Dashboards are limited to Objectives at various levels of our organizational hierarchy. This is very useful but I'd like to enhance the dashboard with additional summary data.

We use a Custom Field on the OKR Board and I'd like to present this field on a Custom OKR Dashboard. This doesn't seem possible - or I haven't figured out how. 

Does anyone know how to include additional fields (Custom or standard) on a Custom OKR Board?