I don't understand why you didn't yet provide this enhancement: LO Calc can already split a document (vertically or horizontally). In Writer it would be absolutely necessary, if you have a long document, as it near always happens. There are technical problems? But why what in Calc is possible, would be not possible in Writer?
*** This bug has been marked as a duplicate of bug 31481 ***
This is finally an INVALID: writing the same request repeatedly: bug 131876, bug 155918, finally this bug 154483.