"stretching" clips.

I am after a functionality where I can take a part of a track, duplicate it and put it on another track and then be able to modify the in and out points of the copied section to include more or less of the original track if I need to.
I come from video editing and this is one simple piece of functionality which video editing always has and I can’t find it in Audacity. To me it’s an obvious piece of functionality to have when working with a timeline but that may be my bias from working with video.
In video editing you have a bin outside the timeline with your unedited footage and then you have clip on the timeline which is taken from the footage in that bin. You can stretch the clip to include footage that is on either side of the section that you have put on the timeline. You can delete half of the clip on the timeline and then stretch the clip about back out again 2 restore the part that you have deleted.
In Audacity when I try to do this it literally stretches the clip to make it longer and lowers the pitch but this is not what I’m after. Does Audacity offer this kind of functionality? I am assuming that it does but I just haven’t been able to work it out yet.

You can stretch audio without changing the pitch via “change tempo”.
( however it does change the quality of the sound: it becomes computery )

Thanks but thats not what I mean. I want to copy a section of a clip onto another track and be able to expand or contract the selection area so the copied clip on the second track gets bigger or smaller

If you mean like this (below), then you are using the wrong program - use Ardour.