Campaigns, tags and folders
They answer different questions. Using the wrong one is why lists get messy.
A campaign
A thing that happened once, with dates: the spring catalogue, the trade stand, the September mailing. Codes, short links, landing pages and forms can each belong to one campaign, and every report can be narrowed to it in a click.
A tag
A label that outlives any campaign: print, retail, north-region, test. Something can carry several. Tags are also where you mute alerts for a whole group at once.
A folder
Filing, for the list itself. Folders are per list — codes, links, cards, pages, forms, media each have their own — because filing a card under a heading that belongs to your codes helps nobody.