When an account is hidden it is no longer included in historical balances when viewing the charts in the Balance or Portfolio tabs. However, this means I can't see the overall historical balance of my portfolio without making a report, which is more cumbersome.
It would be nice to have an option to include hidden account data in the charts when viewing historical balances. For instance, if I click on the Investing or Brokerage items in the side nav I want the chart to be able to include the shares that I had (or have) in hidden accounts in the past, in the same way that it includes shares that I had in the past in non-hidden accounts. Right now once I move an account to hidden (so that it doesn't clutter up the sidebar) it stops being included in the historical charts, which skews the overall view of my portfolio balance over time.