I'd be glad to help share information about adding the memo column on your vendor information.
Are you referring to adding the Memo column on the Vendor Information screen? If so, as of now there isn't an option to add it from there. However, you can add a memo field by clicking on Additional Info of your vendor and click on Define Fields. After, add Memo under the Label column and put a check-mark under Vendor.
On the other hand, please know that when creating transactions to your vendor, there is also a Memo field on the transaction's page.