yes possible ,

you can create parameters in data model but can hide at report level , first create data model with parameter, then create report , edit the parameter tab in report screen,where you have to disable the parameter for the report , assign default value like 'novalue' for the parameter, same value has to be handled by query  ,for this  you can apply logic like ((field_name=:param) or  (:param='novalue') or (:param is null) ),

let me know if you have issue, Thanks