Hi Carolina,

A table is just a display, you cannot add a formula specifically in the table.

If you modify a formula in a table, it will modify the metric. 

For year to date, I’d suggest that you create a dimension called “Period Outlook” with two items: Monthly & YTD

Then you can add this dimension to your metrics and use YEARTODATE() like this:

Be careful when adding a dimension, you will loose data (not formula). You can try in a new metric.