Every budget line, every invoice line and every forecast row carries a cost type, and cost types are grouped in cost categories. That one chart is what lets Tubes put budget, actuals and forecast on the same row.
Structure
A cost category (Crew, Camera, Post-production) contains cost types (Director of photography, Camera rental, Colour grading), each with a code, a name and a colour. The administration format chosen at signup determines the starting chart; Movie Magic accounts import theirs.
Maintain
Under Settings > Cost categories and Cost types you add, rename, recode and reorder. A cost type in use by budgets or transactions cannot be deleted; deactivate it instead.
Colours can be set per category, or imported in bulk from a file with the category ID and a hex colour. See Import lists from a file.
Administrations
An account can have several administrations (legal entities), each with its own ledger. Cost types are mapped to a ledger account per administration under Cost type administrations, which is what the export uses.
Mapping to accounting
With Xero connected, every cost category maps to a ledger account and every VAT rule to a tax rate. Unmapped items block the export. See Connect Xero.
Role scope
A role can be limited to a subset of cost categories or cost types, so a department only sees its own costs. See Roles and permissions.
Note: Recoding a cost type changes it everywhere, including budgets that are already published and exports that already happened. Do it only when you are sure, and preferably not during a running production.