Hi @Jebarkas, thanks for messaging the Community.
Currently, only specific system folders can be backed up to the site, namely those in the Home folder, as mentioned here.
It wouldn't be possible to backup folders from any other location on your machine at this time. However, there may be some other third party apps or services that could help in backing up these other folders to Dropbox.
If you have any further queries, feel free to message back.