SNOM D785 Enable recording button

I have to admit I'm pretty lost and frustrated.
I've got a Snom D785 with the latest firmware (10.1.198.19) and I need to be able to record calls to a SIP recorder.
Using the search function in the help center I found a setting <recording_mechanism> with which
I can supposedly tell Snom to make a call when Recording is toggled.

The only problem I have is:

There is no recording button anywhere.
I then figured this button can be configured as a softkey somewhere
and be shown only during an active call.

After some more or less specific searching in the help center I encountered the setting <call_screen_fkeys_on_connected>
which sounds like it is exactly what I was looking for.

The default setting of the phone is:
<call_screen_fkeys_on_connected perm="">F_LEFT F_RIGHT F_CONF_ON F_HOLD transfer(not:Transfer) F_DUAL_AUDIO(not:Conference) F_DELETE_MSG F_CALLRECORD_CONTROL_ON </call_screen_fkeys_on_connected>

Okay I thought, what does this mean?
F_CALLRECORD_CONTROL_ON sounds like what I am looking for, so again I started searching (and googling) around;
but it was a fruitless effort; I found nothing. What does it mean?

I then figured, there MUST be some kind of clear documentation how to configure this and what the config values mean...
Well... I did indeed find a table in the help center:
https://service.snom.com/display/wiki/Key+Events

But the table seems to be incomplete.
I cannot find F_LEFT and F_RIGHT for example (what do they mean and where is this documented?),
also F_CALLRECORD_CONTROL_ON isn't mentioned either.

Also, from the syntax I could gather that apparently settings can be applied conditionally (where is this documented?).

During an active call the softkeys available are: Hold and Transfer; Buttons three and four are empty; I would like to use Button four for toggling call recording.
I then simply replaced F_CALLRECORD_CONTROL_ON with F_RECORD (which is documented in the key events table) but nothing changed.

Sorry about this little rant, but I found the docs the be lacking;
there's lots of documentation in many places but to me there seems to be no clear line to follow when looking for something specific.

Does someone know how I can enable the record button during an active call
and maybe guide me on how to use the docs (maybe there IS a line I am just missing...).

Thanks folks