Region Deletion

[SpiritRising]

Hi Sherry, thanks for the link to the video on region deletion.
Here's what I did last night -- I'm sure there's a better way if you can help me think it through.

Background info -- this is what I do for my choir over and over again:
- use a program to scan sheet music and convert it to a midi.
- import the midi into Notation Composer.

Problem
Sometimes a 1/8 rest is elongated to a 1/4 rest (could be caused by the scanner or by how NC imports midis, don't know yet). Sometimes a note is truncated so everything still lines up properly, but not always.
This happened in a piano staff of an SATB score.

Solution required
So I need to reduce the 1/4 rest to 1/8 where the time signature is 4/4.
(The piece also has bits in 2/4, 3/8, and 5/8 later.)

Action Implemented...
So, I did the barline procedure from the video, and successfully changed the Rest. Yay!

Oops
However, the entire remainder of the piece was then out of synch -- barlines had shifted relative to the notes.
So I adjusted the next measures manually in order to get them re-synchronized with the time signature changes. I ended up having to do this with every measure to the end of the piece (about 100 measures). That took a long time. Me not so smart I think (maybe my past as a software interaction designer blinds me to the obvious).

In the video, there is a step at 0:45 seconds that is invisible to me -- it happens very fast and I can't see what you've clicked on to get the right effect. Perhaps that's where I'm going wrong.

Could you explain what you're thinking about as you do the steps between 40 and 50 seconds in the video? Can you spell out what mental calculation you're doing when choosing to select notes and do whatever happens a 0:45?
Thanks!!