slows down when running for a while

the editor gets slower and slower as the application remains open longer. it takes longer to update the screen when scrolling. it may be related to number of times switched panes. not sure. have to restart every few hours of usage to continue work. running mac version. note this is new to this version with the new font and redesigned toolbar, previous version could stay open indefinitely with no slowdown

0.20.0

Start by reproducing the slowdown on the macOS version 0.20.0, leaving the editor open and switching panes while monitoring scrolling and screen updates. Compare behavior with the previous version if available. Done means the progressive slowdown is reproduced, its cause is identified, and the editor remains responsive during prolonged use.

Written by the indexing model from the issue text.