Tools you rarely need, but are glad to have when you do. Most are in the Tools menu and in Wallet › Advanced.
A payment shows on a block explorer but not in your wallet? Once the wallet is synchronized, Tools › Import transaction, paste the transaction ID, and click Import. If it belongs to the wallet, it appears in History. Check that the right account is selected.
Tools › Broadcast transaction › From text (or From file) sends a signed transaction, in hex, to the network: through the connected node or one you choose, following your Tor and proxy settings.
Tools › Address checker tells you whether an address is valid, whether it belongs to the open wallet, and to which account and index.
Tools › Tx pool viewer lists the transactions waiting to be included in a block, as the connected node sees them.
For developers and testing, start Biscuit with --stagenet or --testnet. Coins on these networks are worthless; never accept them as payment. A stagenet faucet gives free test coins.