Dear Khanal,
the NA appearing as variable is a bug. it has been fixed and will be released with the next version that is currently under testing.
Yes, you can specify condition. the third column of the CSV file is exactly that.
However, in your case, the last row should contain the equation that will be applied when none of the above criteria matches with your data.
At the moment it's not possible to delete an equation list; you can delete a calculation step that is using that equation list if you don't want to use it anymore. the delete of the equation list has been added to our task lists.
Please let me know if this answers your questions or if you need further information.
Thank you,
Mino