This is a real bummer. It’s a SysListView32 and I made a message trace on it but nuthing that look meaningful there.
I am guessing you may be able to check them by sending WM_LBUTTONDOWN with MK_LBUTTON (I noticed right mouse button works too.)
The coordinates for the mouse location you’ll have calculate from the results of LVM_GETITEMRECT, LVM_GETORIGIN, and potentialy LVM_GETITEMPOSITION (not sure as i never saw results from those messages,) iterating through all the items.
This is all theoretical but might work. Other measures might be needed for instance if the list check the real mouse location you may need to place it over the item, which imply you may need to scroll the list to make items visible.