Northmere Events tracks equipment moves separately from its supplier catalog. Some items have two suppliers, a catalog item has not moved, and a movement refers to an item outside the catalog. Both sources also contain a missing item identifier. These are separate questions to investigate, not reasons to force every merge into one row per move.
For each task, decide which population must survive. Matching-only questions need an inner join; preservation questions need an outer join; missing-match questions need an anti join. Expand the catalog key so a catalog-only record remains identifiable. The raw-key tasks deliberately preserve Power Query's exact matching behavior, including its treatment of null keys. Later you will clean a padded key before comparing known items. The final task uses append because it adds movement records rather than attributes.