As Steve points out, the Ctrl/Cmd modifier key is probably just what you want. By default (without a modifier key), PrE will cause all material to the right, Ripple and move. This can become a real issue, if one has added, say a music Track, as it will get split and moved too.
Also, remember that one can have Video (or Stills, etc.) on more than one Video Track. The upper Clip will be the one that is seen, unless it has "holes" in it, or has less than 100% Opacity. If what you want is a Clip (or other Asset) to essentially "replace" existing footage, there is no need to Cut, or Insert. Just place that Clip on a higher Video Track, and IT will be what is seen - no Ripple, etc., and the music Track is not affected in any way.
Unfortunately, PrE does not allow for the Locking of a Track, as PrPro does. That would solve the music Track issue. For that reason, I will only add my music, after all Video has been edited completely. However, I do not do anything remotely like a music video in PrE, so my workflow is easy. Track Locking has been a feature that I have requested, from the first day that I used PrE.