Download a folder from gui client (within a library) without syncing

Is there an option to download an entire sub-folder to windows without syncing the syncing it? (It is important as security and encryption related issues- a synced folder is practically not encrypted on the client’s pc)

Sure thing.
You can either download the folder from the webinterface Seahub (just navigate to the right folder and hit the download icon) or using the Seafile file browser in the sync client (right click on a library, select the file browser, navigate to the folder and download with a right click)

As I said I’m looking for a secure solution that will allow to download a folder without syncing it, because once a folder is synced the encryption is obsolete.
Furthermore, when using the web client in order to download a folder the encryption is obsolete again, because when you open an encrypted folder in the web client the decryption happens on the server side and not client side, ant the server holds the decryption key for an hour- something we want to prevent

I am not sure what you’re driving at.
Do want to download and save the encrypted data locally and then have you desktop apps access the encrypted data? This is not possible. MS Office, Adobe Photoshop, … can’t make use of the encrypted data.
If you want to encrypt your data locally, use hard drive encryption.