Not sure if this is explained anywhere else. There are two places that I can add row rules, one is in the dashboard grid properties, the other is in the customization.
One (the second) requires customizing the form. The other does not.
Ive found that customizing a dashboard can make it impossible to change its core functionality (like adding a field to the BAQ, and then adding that field to a grid). Even just “customizing” a tracker panel in Dashboard Designer.