You can add a column by adding a calculated field.
1. In Monarch Classic, go to Table Design.
2. Click Formula Fields.
3. Click Add (on ribbon) to display the field options. Select
Formula field: if you wish to fill in every row with values based on a specific formula (may not be numeric).
Lookup field: if you wish to fill every row with values based on another field's values, following a specific criteria/format/condition.
Runtime field: if you wish to fill every row with values you set every time you open your project.
User edit field: if you wish to fill every row with specific values by entering it yourself manually.
I hope I understood your need correctly and provided you with a solution appropriate to your need. :-)