[Typo3-dev] Dynamically add Flexform Sheets to Datastructure

[Tim Franz]

Hi there,

I wrote two extensions which I  connect via another extension. 

Background: One extension is about diploma theses and the other one about
university staff. The third extension hooks into each of them and adds
information about supervisors to each thesis (and supervised theses to each
staff member). This all works fine.

Each of the two main extensions are configured via flexforms. Now I want to
configure the 'bridging' behaviour also via flexforms in a way that the
configuration options for the bridge are displayed in each corresponding
plugin configuration.

Question: Is there a way to add flexform sheets to an existing
datastructure? t3lib_extMgm::addPiFlexFormValue does not do what its name
suggests - it does not add but replace the datastructure with the new one. 
Is there a method similar to itemsProcFunc to add sheets? FlexForm
documentation is still quite sparse regarding the advanced features.

If this is not possible: how would you solve this problem? Add another field
in tt_content with the configuration of the bridge and put this into
tt_content's subtypes_addlist? How do I get the values of this flexform
field in my plugin?

Thanks in advance for any hints.

Greetings
Tim