Hello, I would like to know if it is possible to set the default size of the note window, which is located in the ACP on the right (manual setting and saving does not work).

There's no setting or option to change the size of that field.

Hello,
thank you very much for your answer. It is a pity that it cannot be changed, because I have quite a long note and it looks quite strange. I hope that someone will take this into account in the future IPB version.

You can check out Spacious by @All Astronauts, which gives admins a whole section for notes.