In the Edit Mode of the dashboard, click on the 'Open Filters' option on the top-right panel. You get a popup, 'Filters' where you can create any filter(s) for the dashboard.

Click on the plus icon, 'New Filter' and you get an 'Add Filter' modal.

Enter a suitable 'Filter Name'
Choose any one of the 3 'Filter Type' options
- Dropdown Filter
- Date Range Filter
- Checkbox Filter
You can choose to checkmark 'Make Filter Mandatory to View Data' if needed.
Next is 'Select Source Data and Column Name'. Here, all worksheets/reports used for configuring the dashboard appear here. You can choose any specific column from the dropdown for one or more source worksheets/reports to filter the dashboard.

Then, click on the SAVE button to apply. Any filter created is stored in the 'Filters' popup for user reference (refer to gif-1).

Furthermore, you can apply (and remove as well) the filter to check the dashboard view in the Edit Mode. You can also edit or delete the filter created (refer to gif-2 - click on rightward arrow in the preview)

What are View/Edit Mode operations of the Dashboard?