You are asking about "another way to do it". So just wondering, which way have you tried?
From your screenshot, looks like yours is a parameterized data page. If you have to reference it in a data transform, you need to use the decorated syntax: D_RiderPage[detail:"321", relation:"1"]. You can then iterate over the results using For Each Page In D_RiderPage[detail:"321", relation:"1"].pxResults. Note that the values "321" and "1" need not be hardcoded. You can replace them with property references or parameters.
Your syntax seems to be correct. Is your data page and Data transform in same rule-set ?
Just wanted to check if it is not pre-requisite issue and data transform is looking at correct data page.
Also which Pega version are you using ? There was an enhancement few releases back to data pages to take the parameters from current parameter page, since your params are already in parameter page, could you try directly calling your data page without passing params explicitly.
I had created a similar use case with two parameters taking as inputs by the Data Page List and used in the data transform. I doubt you might have missed some configuration, could you cross check with my use case and let me know for our further investigation share your full use case configuration.