We got requests from customers to make validation errors on forms more prominent. Up until now, if you had a validation error on a tab, we would add a red asterisk to the tab name. Customers felt that it was too easy to overlook, especially with larger forms. The Save button would then not work and it would take time to figure out what was going on.
We added a more prominent error sign to the tab name and also a validation summary box under form, listing tab and column names with validation errors, like so:
Hope it helps make forms more user-friendly, just re-save the tab settings to get the latest version.
The change applies to O365 customers only, on-prem customer already received a similar update in one of the latest versions.