Feature Request Offline Effect Processing

Here is what’s confusing me:
If I apply a PlugIn to a clip or region (offline effect prosessing), I can preview the results in the ‘Process Plugin’ dialog.
Now I want to make some changes to the effect - I select my event, go to ‘Offline Process History’, select the effect I wish to change and click ‘Modify’.
Now, the ‘Preview’- button is greyed out - why why why? I can now only guess the parameters I want to change, hit process again and listen to the results, which is not very practical!
I understand that Cubase generates Its own files for offline processing, but if I re-open this dialog, I really don’t see why there shouldn’t be a preview-function like at the first time I applied the effect…

Thanks a lot for your comments!