The editor is not ideal for complex editing,, and for unedited videos with over 100,000 views, saving changes may be restricted (excluding blurring).
It is best used for "emergency surgery" on published content to avoid having to delete and re-upload the video. youtube-editor
The YouTube Studio Editor is a built-in, browser-based tool designed primarily for making post-upload corrections to videos without losing view counts, comments, or changing the URL . While not a replacement for professional software, it offers essential, free, and permanent editing capabilities, including trimming, blurring, and audio enhancements. The editor is not ideal for complex editing,,