Boolean question

You can configure the metadata card to do this. Your rule filter would be "Employee terminated IS Yes" and in the property behaviors you would set "Is Required = Yes" for Date of termination.

Note that your Boolean property needs to use either a checkbox or radio button UI control, the configuration does not work with the default dropdown menu: Metadata Card Configuration: Using Boolean in rule filter So you need another rule that would first set this UI control for Employee terminated property.