Hi Nebo,
If you are referring to the Customer Message from the Invoice Screen, then you would not be able add a new message directly in Method. This is a limitation from Quickbooks, Method is able to retrieve data from the CustomerMsg Table, but we do not have access to write/edit this data back to the Quickbooks Table.
I am not sure what your exact intention is with creating your own Customer Message, but there are some workarounds that you can use. If you are just looking to add a few additional standard messages to the current dropdown list, then you would have to add these messages first in Quickbooks and then they will appear in the dropdown list on the Method Invoice Screen. If you are looking to create a Custom Message for each Invoice, then you could consider using the Memo Field (if you aren’t currently using it for something else) located directly below the Customer Message Field on the Method Invoice screen. The advantage of using the Memo field is that it is a value from the Quickbooks Invoice Table, and will get synced between Method and Quickbooks. Alternatively, you could also create a new custom field, let’s call it “InvoiceMessage”, from the Method Invoice Table then simply replace this new field with the one already on the Invoice Screen (example Screenshot below). The only limitation with making a new field would be that it won’t get synced to Quickbooks. Keep in mind if you do use the Memo field or add a custom field, make sure to update the “Invoice” Report through the Method Report Designer, to show your new field instead of the original “Customer Message” field. I hope this helps answer your question, please do not hesitate to reply if you have more questions regarding this.
-Ben