When using the Account Register Window it is frequently useful to be able to view another account and also the transfer account at the same time. GnuCash allows you to do this quickly by using 'Jump'. This is available Jump icon on the toolbar and in the Actions > Jump menu in the Account Register Window.

Select the transaction in the Account Register Window and either click the jump icon or select Action > Jump to open the Account Register Window target. If the transaction is split between more than one transfer account then you will need to show all the split transfer accounts first and select the transfer account to jump to.