What does the Batch Change menu do?

Right-clicking a group of selected transactions will bring up a context menu, providing only functions that can be applied to multiple transactions. One of these functions is Batch Change, which makes changes to all currently selected transactions. Batch Change allows you to make changes to the Description, Check#, Memo, Tags, Category, and Account fields in the register.

Changing the Category of a transaction changes the information which is currently in the Category field of the transaction. Changing the Account of the transactions will move them out of the current account (or category) register into a different account (or category) register.