Hello Ayush,

According to the instructions, one can only combine marksheets for CBSE boards subjects only.

You can follow the instructions below for getting a combined marksheet for CBSE

Students must go to the university website and apply for the consolidated marksheet there. Alternatively, they might go directly to the university and apply. Students who want to obtain their consolidated marksheet from the university must present a copy of their admit card as well as verification of their college ID.

You cannot combine marksheet for NIOS and CBSE subjects.

Hope that answers your question