write reference qual condition on CI field that based on current category ,related CI should be visible like that 

Create script include and call it from above ref qual by passing parameter as category values

 example : javascript: getCIs(current.category);

    getCIs: function(category) {

        var cIs = [];

        var ciGR = new GlideRecord('cmdb_ci');

        ciGR.addQuery('category', category);

        ciGR.query();

        while (ciGR.next()) {

            cIs.push( ciGR.sys_id.toString(),}

                 }

        return 'sys_idIN'+cIs.join(',')