Is there a way to create an extra column next to the column: "notes"? 

We work together with Payconiq and it would be useful to check if the transaction is made trough Payconiq. I started with applying a new category and use this in "multiple categories", but this disturbs the rapport models ect. 
In our previous Excel file we used for finances we just had another column  where we'd put a P if the transaction was made with Payconiq. I was wondering if something similar can be done in MMEX and if not if you have other ideas how we could make this into a clear overview.