If you add departments, categories, or Dimensions manually in Budgyt and QBO, they need to be mapped from Budgyt.
If you are using Quickbooks Online, and add classes/departments, or accounts/categories, or dimensions, in QBO, they will automatically be created and mapped in Budgyt during your next import.
If however, you add these details manually in Budgyt first, then add to QBO later, you will need to map them from Budgyt before running your next import. If you don't add the mapping, a duplicate department, category etc will be created during that import.
To add the mapping, go to Settings > Manage Departments/Categories/Dimensions, click on the Mapped Quickbooks Class/Account drop down, then choose the appropriate mapping.