If you are trying to set a table and cannot click Set as table because it is grayed out, the cause is likely to be one of the following.​​

• The row contains one or more fields that cannot be included in a table
• The row contains one or more fields that have already been applied to your actual environment

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

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

If any of the above fields are included in the row, delete the fields and try setting the row as a table again.

If any of the fields contained in a row have already been applied to your actual environment, the row cannot be set as a table.
Re-add the relevant fields, then try setting the row as a table again.