May I ask what phone and software version you are using? I have tested this on the office S21+ running Android 13 and I have found a way to back up this. To do this I launched the Samsung Secure Folder> Menu (3 dots top right)> Settings> Manage accounts> Add account> Select the account you would like to save the data to and ensure that Auto sync Secure Folder data is enabled.
yes Unfortunately back up for Secure Folder was discontinued early 2021, can restore back ups which were taken before the change . Whilst possible to back up for instance to local storage not as straightforward or the same level of security. Some information here https://mobiletrans.wondershare.com/samsung-secure-folder
I do not work for Samsung or make Samsung Products but provide independent advice and valuable contributions.
My Device- S21 Ultra 5G ( SM-998B/DS ) CSC= BTU , 12GB/256GB
One Ui 5.0,Android 13 .