how to add meta data everytime in the table

You can create a formatting/casting rule for the CDT and use it before writing the data into DB. This rule will add default values for metaData fields i.e., true, now(), loggedInUser().

I typically create an expression to setup the basic data structure and use it either before or after user data input.

I would recommend always isolating the Write to DSE model in a separate process and using it as a subprocess, exactly for this reason. If you have this, then you can just a script task before your smart service and use it to set the meta data.