Hi,
I do not know how to write a note that lasts 4/4 while the top melodic line changes to 2 2/4 notes.

I don't think you can, in terms of display; however, you can extend the length of the lower G to continue playing across the E and the D above it. Just click on the third little button (to the right of the one you clicked to edit the notes), then right click on the G and extend the blue line to match the end of the D. It will sound correctly; however, it won't look right.

If you're only worried about how it sounds rather than how it looks, you can go into Piano Roll mode and make the change there.

The Notation view will be incorrect, but the sound will play back properly.

That's exactly what jford suggested, but with different words.

thanks jford and dcuny