When a user-defined filter is created, it is added to the list of UDFs that can be viewed using the filter icon in the left panel. It is then possible to edit and manage the User defined filter using the menu that appears when clicking on its name.
UDF icon
Choosing this button will display the User defined filters available in this report.
Move the filter to the "Filter" section to include it in the current calculation (this can also be done by dragging the filter and dropping it in the "Filters" section).
Editing the User defined filter is also possible by clicking on the UDF as it appears in the section "Filters" and choosing "Modify user-defined filter".
Choosing the option "Remove from table" will remove the UDF from the current selection, but will not delete the UDF itself - it will stay in the menu in the left panel to be used in other calculations.