Give a lockdown user access to Local folder

Hello,

I would like to give access to a user in lockdown mode to save a file in specif folder and give access to this folder allowing the user to upload and download files  

That is not a problem. You will need to create a new partition on your hard drive (other than the "C:\" drive), then move the users Library folders (this is easy in Windows 10) to that new drive. They will then have access to the folders in any app they are using.