You can enter the item memo at the same time when you create an open item shown below:
In case the person may not enter the memo or forget, there is a setting to control
- ALLOW EMPTY: Allow to add an open item without memo
- ASK AGAIN IF NOT ENTERED: If the memo is not entered it will popup a keyboard to enter the memo again. However, the user still can close the keyboard without entering the memo and finish the open item.
- REQUIRED: If the memo is not entered, it will popup a keyboard to enter the memo. If not entered, it will not allow to finish the open item.