Trimming a rendered clip SHOULD NOT need to re-rendered entire clip again!
When a clip that requires rendering (red bar in timeline) is rendered, and then trimmed shorter, why does the clip need to be re-rendered? Shouldn't the app understand that it is using a previously rendered clip that has media generated already? When I do green screens, I will often use Neat video denoise effect, which takes a long time to render. I don't have the time to wait for it to re-render the entire clip, many times several minutes long, if all I want to do is trim a few frames off the heads or tails.
Pruth Shankarappa commented
While we look into this issue, meanwhile, does render and replace with effects burned in to replace that source/section work for you?
If you did it then Premiere Pro will be using a rendered clip with Neat video denoise effect burned in and so it can playback real time even after trimming that rendered media.