Creating template parts through the site editor requires saving changes and reloading the editor before new template parts appear in the block inserter. The registration process isn’t instant.
When exporting template parts using Create Block Theme or core export functions, the template part files export correctly but theme.json isn’t automatically updated with the templateParts registration.
You must manually add template part registration to theme.json’s templateParts section to properly associate files with areas. Without this step, template parts won’t display with correct icons or area organization.
This manual step is currently necessary for the template part system to work correctly. The export process handles file creation but not the theme.json configuration that makes everything function properly.