Think Bigger From Filmora User Guide

Change Playback Quality

To ensure smooth playback while editing, you can adjust the playback quality. Look for a small drop-down button above the playback window that lets you change the quality settings.

You can transition to 1/2, 1/4, 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.