Can confirm, this patch worked and resolved the issue.
I've attempted to rewrite this JS so that the reading and writing are batched. This seems to improve browser performance.
Chrome Devtools performance
Attached is a patch for Drupal 10.1.x → AND 10.2.x → . There's some changes to the file between 10.1.x and 10.2.x. We're still on 10.1.x so I patched them both.
ZHawkins → created an issue.
My attempt at patching this.
ZHawkins → created an issue.
Fixing the patch file number.
Rerolled patch from https://www.drupal.org/project/ckeditor →
ZHawkins → created an issue.
Rerolled patch against 9.5.3.