Patient Calendar in Healthcare Dashboard

So the patient dashboard has a potentially useful feature of showing a calendar representation of consultations. Unfortunately in my testing nothing ever shows.

The Consultation Doctype does not show a field for “timeline” (is this where such things should be declared?).

I endeavoured to set this to consultation date but was told that this can only be done if the document becomes custom…I am a bit nervous of that as I do not fully understand the consequences.

Advice please?