Split data of an account in two different synced local folder [on different HDDs]

I have a problem with an account who has a lot of data that need to be kept in sync.
She has simply stored a large amount of data on the Nextcloud server and now wants to keep everything in sync with his laptop. Unfortunately she ran out of space [on the laptop], so decided to buy a Kingston Data Traveler Max and split the hosted data between the internal and external disk.
Her goal is to keep the most frequently used server data in sync with the default /Users/jamie/Nextcloud local folder and the other data on a newly created …/Nextcloud2 local folder on the Kingston dataTraveler.
Unfortunately, she failed because when she tried to do this, she got this error: "You are already synchronising β€œ/” which is a parent of β€œ/Data2020”.
Is this a limitation of the current Nextcloud Desktop App? Is there a workaround?
It’s not clear to me how she can create another local sync connection on a different local disk then add there the folders that are in his home in the Nextcloud server but not currently in sync with her default local sync folder.
THX for any kind of advice.