Q1) Please explain the relationship between dashboards and universes.
Q2) Can we save a universe for a dashboard. I believe that this is not possible at this time.
Q1)
A Universe is created to restrict a data set and not used to restrict dashboard visibility.
Each universe is configured with a source ,agents, etc. in the Metric Source section restricting the data.
Q2)
Yes, that is correct. There isn't anything like save a universe for a dashboard.
If required it can be raised for an enhancement.