As SanthoshMothe mentioned, pxConvertStringToPage can be used.
Syntax: @(Pega-RULES:Page).pxConvertStringToPage(tools, TargetPage, .JSONString,"json").
It can be called from activity or Data transform. json string should be in double quote.
Make sure to have Page-New step for TargetPage (If activity), Update Page step for TargetPage and initialize a dummy property like pyTempText (If data transform), and have it defined in Pages & Classes tab.