We have many customer asking for this.
Typically customer uses input field or drop down list to select a value, then he wants to use this value in filters.
Currently filters can only by set by fixed values, customer wants to use values from document properties on filters in order to control filters from text area easily.
One can put filters in text area but it's not as flexible as the available controls, e.g. input field for entering any values as start date, end date, etc.