On the left-hand side of the Timeline Window, and included as part of the Smart Tool, you'll find the red arrow that points to the right as well as the yellow arrow that points to the right. Together these two features are called Segment Mode. This is because they are a separate mode of operation. The red arrow is the Lift/Overwrite Segment tool. As its name tells us, it contains both of those editing abilities. The good news is that this tool can never alter the material that is downstream of the edit points causing them to go out of sync. This is because:
At the original location from which the segment(s) is removed, it performs a Lift that leaves an equal duration of Filler behind
At the new location where the segment(s) is placed, it performs an Overwrite that replaces (covers up) the material that was previously there
Then we have the yellow Extract/Splice-In Segment tool. As its name suggests, it contains both abilities:
At the original location...