You may be looking to add notes or memos to a particular gift or fund. This sounds like something that you could use the "Donor Memo" feature for!

While this can't be linked to a specific fund, you are able to enable this globally for donors so that they can let you know the details of their gift. Here's how you can enable that feature:

Donors will now be offered the opportunity to include a memo with their gifts. This will show up on all of your exports and reports in the Giving Dashboard.