You can preview a message that will be sent using Memo to see how it will look with all the field codes replaced by the actual data. This can be done from the Message Schedule screen accessed by using the 3 dots menu for each invitation and choosing View/Edit. Then within the Message Schedule screen use the 3 dots menu for the message and choose the Preview Message option.
In the preview screen, any field codes used in your message will be replaced by the actual data, so you can see how the final message will look when it is sent out. Note that you can’t make any any edits to the message from the preview screen, any changes need to be made on the message template or invitation data.