How do I connect Dropbox to Storage Studio?
Short answer: Open Cloud Accounts, click Add Account, choose Dropbox, type a nickname and click Open browser to sign in. Sign in on Dropbox's page and approve access. The Dropbox app isn't required.
Open Cloud Accounts → Add Account, choose Dropbox, give it a nickname such as personal-dropbox, and click Open browser to sign in. Sign in on Dropbox's own page, approve access, and the account is added.
Your Dropbox password goes to Dropbox, not to Storage Studio. Once connected, the account can be used in Data Transfers, Data Parking, scheduled transfers and Data Backup, and appears in the Storage Studio location in Finder. You don't need the Dropbox app installed.