If you use a Custom Load Method (CLM) to get information for a collection, the button Get More Rows “>>” in the Actions Menu is disabled. This behaviour is intended and it will not change, even when you set the Standart Operation of Navigate for the corresponding IDO with the CLM.
I have made investigations on the case and came acros the official CER 146976 of SyteLine, that the feature is intended to be implemented in SyteLine version 9.01. onwards. The CER is linked in the main knowledge base article about the issue KB 1125339 on InforXtreme.
The problem can be currently solved only by increasing the row fetch count.