All beta users now have access to a new page which allows you to categorize transactions by their merchant name. Working from left to right or right to left, you’re able to select one or more transactions grouped by their merchant and a category, then click categorize. Drag and drop is also available, for one or groups of transactions too!
This will allow you to quickly categorise a large number of common merchants more efficiently, meaning you can get on with other tasks. Become a beta user and give this a shot via Manage > Categorize by Merchant!