Thanks for raising this.
Unfortunately, SmartSheet does not have a row-number on the API. A row actually has a GUID and we're translating that to a dropdown with row numbers.
The value behind that row number is actaully the GUID. So, we could allow you to use variables, but then you'd have to use the GUID.
Would that also solve your issue?
It would be great if you could provide more details on what you're trying to do.
Thanks Brady for providing the scenario.
We had a look at this again and it is something that will work, so we're planning to make that change and allow you to use a Row ID in the Row Number field.
BTW - i said it was a guid in the previous response, but it's actually a unique number/ID.
Example scenario of where this is needed:
1. Add a row action adds a row to SmartSheet using values from a Nintex form.
2. User makes changes/additions to that row in SmartSheet
3. After a certain amount of time (or a completed task), Nintex workflow uses the "Get a Row" action to get the current values of that row, using the GUID returned from the output in step 1.
Unfortunately, you can't insert variables into this field. At the moment, I need to use Update A Row actions, simply for the function of getting a row.