To create an account group on your iOS device, please proceed as follows: 

'Settings' > 'Account Grouping' > 'New Group'

Alternatively, you can create a new account group directly from the account list:

'Accounts' > 'tap and hold on an account' > 'New Group'

You can now enter a name for the new group and add accounts to it.

Banks that show a small folder symbol in the Group Management already belong to another group. If you assign them to a new group, they will be removed from the previous group.