I pretend to change from one provider to another, but i have various configurations (folders) set on the nextcloud client.
Is there a way i can set the client to: instead of sync to this address sync to that one (but keeping all the client’s present configurations, and uploading all the files in the sync again)???
There is no official switch (I think). To make it work without a new sync, you first have to migrate the Nextcloud to the new server (no new setup). Then you can stop the client and manually change the host name in the Windows-configuration file: https://doc.owncloud.org/desktop/2.2/advancedusage.html#configuration-file