The backup notes are saved in the backup info file and it is included in the backup tar.gz file since Softaculous 4.3.4
So if you are using Softaculous 4.3.4+ the notes will be available even if you have deleted the backup via Softaculous and the re-uploaded it.
>> Concatenating domain name
I will forward this to the development team and see if they can add it. We currently use the installation id.