I created a named formula in the canvas that pointed to the parent row’s column and then referenced it from the table. This is because thisRow in the table refers to the canvas table and not the parent table. parentRow did not work in this scenario.
If you set things up this way, you can also keep around a templated canvas like in the following example. It’s a hack and it is not pretty but it works:
The trick is to build a canvas column with working formulas that reference the table columns you need. Then copy and paste that column value into its own “template” page which will have broken formulas. Then set the value for new row to be that “template” page.
I would not recommend doing things this way. I’ve moved away from using canvas columns with formulas because it is a hack that I’m not sure will always be supported in Coda.