How to select multiple transactions

I had an investment/mutual fund account converted to a new account. I want to move all the transaction history to the new account, which is in effect what they did. I am able to do it 1 transaction at a time, by clicking the account name and picking the new one out of my list. But I think there is a way I can select multiple transactions? I see a Move transaction(s) in the context menu but I can't figure out how to select multiple transactions. Can you help? Thanks!