It'd be cool and provide more flexibility if something like --only-ticks-under was implemented (similar to --only-ticks-over)
For example, I'm interested in seeing the info only on 50-80ms ticks, but right now Spark doesn't provide such functionality.

I'm not sure why this would be useful - why would you want to limit a profile to not include laggy ticks?

There is a situation where I encounter two types of lag at the same time - 50-80ms and 100+ms.
If I profile using only-ticks-over 50, the resulting info gets blurred and it becomes harder to clearly distinct 50-80ms from 100+ms.

But both are causing lag right? There isn't really a good reason to need to separate them out in profiles.

If you don't find this request reasonable, then it's all good! I won't argue.
I'll fork Spark and implement this myself for personal use when I have time.
Thanks for the feedback, anyway.

No worries, and sorry, I didn't mean to come across as argumentative!

Was just trying to make sure I had understood the reason for your request. I do think though that this functionality is a little too niche for inclusion in spark itself - hope you understand :)