OK. I solved the less important half. Below I wrote my solution (not automatic) and I dont have idea if TwinCAT can help using EDS files. If you have any information how to make it automatic please let mi know.

And I still dont have idea, how to select automatically the instancs I want to see instead of the default instances (set in section [IO_Info]/ default in EDS file)

Lets go! :

•  connect cables, supply etc (electrical stuff)
• In TwinCAT in I/O devices click SCAN and press ok few times 😉
• now (in tree on the left ) you have something like Device 3 (EL6752)
• press RMB on this element and select ADD NEW ITEM
• select miscellaneous/DeviceNet Node
• TwinCAT asks about EDS file - select it.
• Now you have Box with some number and description "(DN Node)"
• Remove inputs and outputs
• press RMB on inputs and add new item
• Look in EDS file - add first data in active instance: name it, select address and datatype and press OK
• repeat it for every data in instance (CIP Volume 1 and CIP Volume 3 is the DeviceNet Bible - there are standarized tables for instances in DeviceNet. Custom instances should be described in manual of your slave device)
• Now do the same with outputs.
• Now Save it as the XTI file.
• Voila! You have just made something, which should be done by some kind of script. If you dont know any automatic solution I will try to write it in Python or C++.

So partially it solved, but if device has 10 instance options for input and for output it will give you 100 of XTI combinations. XTI is just simple XML file, so parsing is easy, but somebody have to do it 🙂 

Like I said - If you know how to do it automatically, please let me know!