In contract control, you can enter any notes under Note and save them with Save note. You can change or delete your note at any time by adjusting and saving the text.
Your note is only saved in the contract control for the respective contract document or the contract file. Unlike the contract notes, your note is to a certain extent "volatile". If someone else changes the note, your note is simply overwritten. There is no history or restore option.
If you want to permanently save a note on the contract document or the contract dossier (file), use the contract notes: What is the "Contract notes" section in contract control used for?