I am looking for a way to create an \"Imports Newtonsoft.Json.Linq\" in my SSIS script task, but this is apparently not as simple as a \"manage NuGet Packages\" in SSIS. So
Not Possible.
If you add any third party library(.dll) file, the SSIS will run inside the visual studio(local). So, in local it will work fine (while running in Visual Studio). But once you run it through the SQL Server Job/ETL, it will not.
The only way is you need to add your third party library/libraries in "GACUTIL" of the server where your SSIS is running(through SQL-JOB/ETL...).
As you have mentioned, you are using "Newtonsoft.Json", so, copy the Newtonsoft.Json.dll to the server (gacutil) where SSIS package is running.
Try this and let me know if you face any issues