When used with XTR.OPCODE 4 (select from existing control), defeats all redraw/refresh of data, which makes for a "cleaner" re-entry, assuming that none of the parameters which might affect the display have changed. Without this flag, re-selecting from an existing control will reset the columns, possibly adjust the vertical scroll, etc. The sample program XTRA3 demonstrates this.
Note that it is possible to use the XTF_NOREDRAW flag along with opcode 4 (reselect) even when you are updating data in the editable cells prior to the reselect. In early versions of XTREE, XTF_NOREDRAW disabled the updating of the editable cells from the ansary parameter on reentry. XTF_NOREDRAW might be useful in this circumstance to eliminate unwanted display adjustments taking place during the reentry process.