There is a discrepancy to build a Url() from a row. It looks like table.First() is a row, but actually we need to call First() twice to get a row on which we can call the Url() function.
However, the formula editor does not know, from the type point of view, what we obtain by calling First() twice on the table.
Let me know if this is clear enough as a problem description
I found it very useful to use OpenWindow with a row URL. That’s terrific !