If you are trying to set a table and cannot click "Set as Table" because it is grayed out, the reason might be one of the following.

• It contains the field which cannot be set as a table
• It contains the field that have already been applied to your current environment

If a row contains the following fields, it cannot be set as a table.

• Label, Related Record, Blank space, Border, Group, Record number, Created by, Updated by, Created datetime, and Updated datetime

If any of the above fields are included in the row, delete the field first and check if the row can be set as a table again.

If a row contains the field that has already been applied to the actual environment, it cannot be set as a table.
Add fields again and check if the row can be set as a table again.