• Improvements to the UI when a fatal error occurs, including an admin toolbar warning.
• Improvements to the UI when QM is running in "broken" mode due to missing jQuery or an unrecoverable JavaScript error.
• Don't display fatal errors if error display is off and the user cannot view QM.
• Improvements to the visual appearance of the wp_die() output.
• Simplify re-throwing a caught exception so QM doesn't get the blame for fatal errors, eg. in the WordPress core fatal error handler.
• Add support for logging a variable of any type in the logger, as a replacement for var dumping.
• Don't show a message for errors in Ajax calls that have already occurred on the main page load.
• Don't dispatch QM during an iframed request, eg the plugin info modal or an upgrader action.
• Hide QM itself from various panels by default to remove noise. Can be controlled via the existing QM_HIDE_SELF configuration constant.
• Support for the new is_favicon() conditional added in WP 5.4.
• Fix the side panel resizing functionality.
• Add a WP-CLI command for creating the symlink to the db file.
• Add filters to QM_Util::get_file_dirs() and get_file_component() to allow support for non-standard plugin and theme locations.
• Add an action that fires when QM enqueues its assets, so add-on plugins can enqueue theirs only when necessary.