My DC has just opened a Lifetime ISA to enable them to pay the full £4000 for this tax year. It's not clear whether they need to close their Help to Buy ISA? They don't need to transfer the money, as they have enough in another savings account.
I've tried and failed to find a definitive answer. They realise they can only use one of these ISA's when the time comes to buy a property (years off). It's likely the LISA will have more money in it by then.