Hi @garthh
In the original post it said "Is there a quick method to write to excel via List or Datatable?"
For this use the "Write to Excel worksheet" action. You dont have to worry about how many rows the list or datatable has. All the rows of the list/datatable will be written to those many rows of the Excel sheet.
But now I think you are asking "how can a list be made to fit the rows?"
"The number of rows vary each time a spreadsheet is made"
"Get first free column/row from Excel worksheet" will give you the total number of rows on a sheet but I am not clear why do you need this when you are writing a list or a datatable to a sheet.