Hi,
thanks for your post, and sorry for the trouble.
Just to be sure that I understand: That mask (“SRN-“) should already be prefilled in the column on the “Edit” screen, and the user who enters the data should only have to add the number, and can not remove the SRN- prefix? That’s not possible at this time, sorry.
However, it would be possible to automatically add this when the table is shown to the user. So, the admin would only add the number to the column and SRN- would be added automatically on the frontend. This would require a bit of custom code that I could find for you as part of the priority email support that comes with the TablePress premium license plans.
Regards,
Tobias