Thanks, but unfortunately your suggestion didn't work for me. Perhaps it's due to something in MCUXpresso. Your suggestion resulted in attempting to open another instance of MCUXpresso, which failed because the associated workspace was already in use by the prior instance of MCUXpresso.
These are the command lines I tried (for grepWin) (ensuring the IDE was closed first).
C:\nxp\MCUXpressoIDE_11.4.1_6260\ide\mcuxpressoide.exe -name Eclipse --launcher.openFile %file%:%line%
C:\nxp\MCUXpressoIDE_11.4.1_6260\ide\mcuxpressoide.exe -name mcuxpressoide --launcher.openFile %file%:%line%
While they both opened the IDE, neither opened a file in the IDE.