But now, I realize it's not for the purpuse I intended. I wanted to create a kind of "view" in Reportportal, to use it the report results. Not in a filter of the report
Please try "SQL View" report type. You should be able to create by clicking the Design toolbar button of any SQL report. Any SQL report (that is not stored procedure based) can be used as a template.
You can also enable "SQL View" report type under Admin > Design menu.