Think Bigger From Filmora User Guide

Change Playback Quality

For smooth playback during editing, you can change the playback quality. Look at the area under the playback window; you’d see a small drop-down button that allows you to change the playback quality.

You can transition to 1/2, 1/4, 1/8, 1/16, or else stick to full quality. Let me explain if this seems confusing; 1/2 means half the playback quality and 1/4 means one-fourth of the original playback quality. In my experience, changing full playback quality to half the playback quality does the job.