Categories organise what money was actually spent on. Behaviour (regular, variable, irregular, one-off, exceptional) and essential/discretionary are recorded separately on transactions.
Main category:
a broad area such as Trading Expenses,
Food & Drink or Transport.
Subcategory:
the useful reporting level underneath it,
such as Trading Software or Prop Firm Fees.
Archiving a category preserves all historic
transactions. It simply stops the category being
offered for new transactions.