Sales Order > Related Records tab > Add the Memo Field in the Sublist

Since the standard Related Records list in a Sales Order is not customizable, create a custom Saved Search that pulls up the related Transactions of Sales Order and set that as a separate sublist.

I. Create the saved search:
1. Navigate to Lists > Search > Saved Searches > New.
2. Select Transaction.
3. Under Criteria tab, add Main Line and set it to True.
4. Under Results, add Memo.
5. In the Available Filters tab  add Created From field.
6. Set the Show in Footer = F.
7. Click Save.

II. Set up the search on a custom sublist:
1. Navigate to Customization > Forms > Sublists.
2. Under Transactions tab, select the search created in Step I.
3. Enter Label name.
4. Set Tab = Related Records.
5. Under Applies To > Sale = T.
6. Click Save.