Batch Change

When you right-click (Ctrl+click), this will bring up a context menu providing functions that can be applied to the selected transactions.

One of these functions is Batch Change, which allows you to make changes to a single transaction, or multiple transactions at once.

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 will change the information which is currently assigned to the Category field.
When using the Batch Change option, the accounts list will show only accounts containing the same currency as the account you want to move transactions from.
Changing the 'Account' of a transaction will move the transactions out of the currently assigned account, and into the specified account.
This DOES NOT create a transfer between the accounts; the transactions will simply be moved to the new account location.