Might be possible
var grd=dijit.byId('mxui_widget_DataGrid_0'); grd.set("selection",["20547673299878420"]); grd.update
Have not tested this on multi select [tpl]grids but it does seem manipulate the current selection widget attribute and updates the widget dom
You will also have to use
grd.get("selection") in order to get the selection.
With this in place you have to write a widget that interacts with the grid and populates some entity with selection objects via the JS crud api and set up the appropriate tables in Mendix
Good luck (when you’re done put it on GitHub)
I think this is not possible out of the box for whole page loads. Maybe it is possible to create your own page selection? You would need something like a wrapper object, an object to point and store the selected entries which is toggled for list items you clicked on and apply custom styling to highlight the rows where the boolean is true? Not that easy, I think