I've tested this in PP 23.2, 23.1, and 23.0 all seem to have this same issue. I'm on a Macbook Pro M1 Max 32GB with my media on an external SSD that reports 2.5k+ MB/s when tested. I've closed all other apps to ensure it's not a memory issue. I don't see any large spikes on Activity Monitor when this happens.
Here's a video of the issue: https://vimeo.com/800713336/dcb5b66d6e
You can see that performance is fine as I scroll around the timeline and move clips but as soon as I trim a clip it lags big time and then every other action lags for a short time after.
Steps to reproduce:
1. Create a new project importing 4k footage.
2. Create a new sequence. Mine happens to be 9:16 1080p sequence for IG Reels.
3. Drag one of the 4k videos into the timeline.
4. Attempt to trim the clip.
I expect that PP doesn't lag when doing that. In actuality, it lags.