How do pre-fill fields in a form invoked via "allow new entries" + control

How do pre-fill fields in a form invoked via "allow new entries" + control

Single or Multi-select relationships are great... and the + button is useful for adding new data into a related form. However it would be REALLY useful if fields in the related form could be pre-filled with data from the parent form? Also, you cant select related records in the picklist and view/edit them... you have to go find them in the associated report (for the related form) and edit them there :(

or...

When using sub-forms is there a way to control which fields (in the sub-form) are included in the sub-form field of the parent form? I cant find any way to limit which fields are visible and it makes using any form with more than 2 or 3 fields useless as a sub form!