In case a Group is hidden and you want to show it on the left menu of the Transaction page you can choose to show it on the Chart of Accounts.
Sign in to Bkper.
Open your book.
Go to the Chart of Accounts.
Look for the light gray hidden Group on the left menu.
Click on the three points next to Group name.
Select the "Show"
The Group is now visible again on the left menu of the Transactions page.