No problem asking a repeat question, especially when you’re polite enough to search first. I was just bringing you up to speed on the history so you aren’t too dismayed by the lack of responses.
There is a feature you may not have used too much yet. Shotcut supports ripple editing, both for a single track and for all tracks. Click the bullseye icon on the Timeline window to turn it on for a single track. Right-click the open space in the Timeline window and select “Ripple all tracks” if you want movement operations to affect all tracks. When ripple is turned on, if you move a clip, all the following clips get scooted with it as if they’re glued to your clip. So yes, you can move a clip to the right without needing a gap to move into. And yes, you can move a clip left without creating a gap. So the extra request you didn’t make is already implemented. 
To be honest, I like your idea. It doesn’t change existing behavior in a negative way and it does make the feature more useful. But I use the phrase “more useful” very loosely. The single-track style of video editing becomes very restrictive the moment a project becomes even moderately complex. Consider this sample project:
V2: Logo with transparency-------------------
V1: Clip1 1&2 Clip2 2&3 Clip3 3&4 Clip4
Now let’s attempt two simple (in theory) modifications to the timeline:
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Swap positions of Clip2 and Clip3. This is going to affect every transition. Also avoid messing up clips or timings on V2 or above in the process. This is difficult to do even with your proposed improvement.
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Lengthen Clip2 by 10 seconds. The transition will be modified instead of the clip length, even with ripple turned on. Unless I’m missing a feature, I think you will have to delete 2&3, scoot Clip3, lengthen Clip2, then rebuild the 2&3 transition. And if anything goes wrong, the undo/redo feature is extremely buggy when transitions are involved. The broken undo issue more than anything is my biggest personal reason to avoid single-track editing.
So that’s part of why this feature request doesn’t get more traction. You’ve got a good idea and it helps, but there are still a lot of common problems it doesn’t fix, so people generally use other methods that work better. I’m not trying to rain on your parade… I’m just trying to provide you with options that will scale to complex projects more easily.