Data split for separate numbering

I'm trying to make work separate numbering using data split functionality. I have made additional common attribute and added it to the objects I want to apply split.
How could I use splitting without defining it in Session parameters, so I could just handle different numerators for every split?
I do not want to use prefix because I am already using it for another reason and it looks complicated with all prefixes.
I also want to use data split for restricting objects, so it will probably serve for two reasons. For this purpose it is obvious to use Session parameters.

1. So, what should I put in session parameters to make all objects visible? If I set ParameterUse Attribute to False splitting does not function and the numbering does not use splitting.
2. Usage of splitted data should be set to "independed and shared"?
3. Do I need to use conditional split for this, if so, how?
4. Is it possible to display common attribute in form which is used as a split attribute or should I use any other attribute as a conditional split to make it possible to make a selection for the user?

ANy help, please. Documentation is really confusing.

I suggest you increase the document number length and include the required separation into numbering schema, for example:

XXYYZZNNNNN where
XX is infobase node code
YY is company code
ZZ is document group code
NNNNN is document number