How to use field type "Storage Format"

[Ralf Weidauer]

The field type "Storage format" is said to hold and render the storage format.

Whatever I tried only a textarea field is displayed.

I also tried to set the value by definition rule like strg_frmt_fld=<ac:structured........> (where the latter is a valid storage format), but then textarea field containing the storage format is displayed.

Maybe I got the purpose of the field type completely wrong, so I would highly appreciate if anyone having experience with that field type would share his knowledge.