Problem description: in Zabbix 6.4 some additional spacing is observed between the widget configuration form header and the top of the dialog. In the below gif You can see the difference when comparing with Zabbix 6.2 release (in 7.0 it is the same as in 6.2):

P.S. the same behavior is observed in the Related reports dialog (where the list of reports that are related to a dashboard is displayed).