Thanks for this Rincy. Most of these operations are analogous to what we have for ArrayList in java. I can always do almost any operation in an activity. However, my question is more inclined towards an OOTB function or API to say perform group by on a pagelist without having to do it in java step in an activity.
In OOTB, I see there are activity namely AppendToPageList, RemoveFromPageList, pycopyRowPageToPageList, etc.. And as functions, they are pxDataManipulate pxReorderPageList, Utilities pxSortPageList, etc..
Would Report Definition help at your end. Refer pxtest Report For Page List. SQL operation can be performed based on the class containing the PageList.