Hi Learn It,
The strategy is to have your condition to be written with an OR and one of the clause to be the FilterVar = its default value so to ignore the other condition.
If your filter is of type Text, set your filter to: FilterVar = "" or <YourOriginalFilter>.
If your filter is of type Number, set your filter to: FilterVar = 0 or <YourOriginalFilter>.
If your filter is of type Identifier, set your filter to: FilterVar = NullIndentifier() or <YourOriginalFilter>.
Example for a filter of a client id, if FilterVar = NullIdentifier() or Client.Id = FilterVar.
Regards,
João