How to remove footage in timeline before starting point

Squamish ed wrote: Interesting. It looks a bit like the effect you get in the precision editor. Wonder why?

I wouldn't read too much into it.
Probably, both situations share the same 'display routine', and a line of code, for this exception "if clip starts before 00:00:00, don't display' is missing… Just a flaw… I send a feedback to Apple, for me, this is no real bug, just 'cosmetics' ....

I think it's really useful as is. If you trim the start of your Primary Storyline, thus your Timeline as a whole, back and there's connected clips that will get truncated, heck, I'd like to know that! I want to be shown I accidentally cut off some of my footage I originally had there. It is a great feature to have as is! Otherwise folks would be complaining that when they trim that first Primary Storyline clip back, they wonder what happened to all that other connected stuff they had a few minutes ago. This way, you see it. It is how Compound Clips work, showing you what is and ins't included in the Timeline they've been placed inside of. Seems very constant and useful to me.