TransactionManager is a tool for manager uncommitted cells, you can send_transaction via this tool and get uncommitted outputs by collector.

const TransactionManager = require("@ckb-lumos/transaction-manager");
const { Indexer } = require("@ckb-lumos/ckb-indexer");

// generate a new `TransactionManager` instance and start.
const indexer = new Indexer("http://127.0.0.1:8114");
const transactionManager = new TransactionManager(indexer);
transactionManager.start();

// now you send transaction via `transactionManager`.
const txHash = await transactionManager.send_transaction(transaction);

// you can get uncommitted cells by `transactionManager.collector`.
const collector = transactionManager.collector({ lock });
for await (const cell of collector.collect()) {
  console.log(cell);
}