How can I start off-block transaction in LoafWallet? Lightening network promise, basic principle is, transaction not need to add to blockchain but cumulate them and submit all together for a reduced amount of fee. How can I choose such an option in LoafWallet? I have not seen such an option in the app.
Lightning Network is not even live and therefor not supported yet.

Actually the Lightning Network does not quite work as you described.

You create a opening transaction which locks the funds in a multisig with the other participant. It's possible to withdraw the funds only after a specified time or to sign a transaction which pays both participants according to their needs and is spendable earlier.  If both participants agree, they sign the transaction.  The channel can then be closed by broadcasting the transaction or they can continue to keep creating a new version of the transaction with pays them different amounts depending on their needs.

This means you can have nearly unlimited transactions for the cost of one opening and one closing transaction.

However this is not live on mainnet (not for Bitcoin, not for Litecoin) and LoafWallet doesn't support it yet.