All users except for collaborators in all paid accounts can filter tasks in dashboard widgets, provided they have full or editor access to the relevant dashboard.
Widget templates that can be filtered:
Active Tasks by Assignee
Tasks by Status
When creating a widget, select a filter from the filter panel on the right. The list of available filters is given below.
To apply filters to existing widgets, click the three-dot menu button on the widget and select Edit.
The type of filters you can add depends on what's displayed on a widget and are detailed in this table.