How to send XEL from Heatwallet to Bittrex. Bittrex says must have a specified message included, but from Heatwallet there is no such a space. and where to put the Xel address
Don't do that, as far as I know heat is sending the message encrypted while Bittrex wants it to be unencrypted. There's a chance you will lose your XEL.
You need to send your XEL from heat to a local wallet and then send them to bittrex.