This question is related to the Sticky submit button at the top and bottom of the form?, and Submit button on top of the long form but I consider has other nuances.
This is what can be seen in a standard monitor:
And this is the complete form:
At the top of each column, I have a button that allows the user to check or uncheck all, so the user can just uncheck all items and send the form without the need to scroll down to the bottom.
So I thought the most convenient is to place the submit button at the top of the form to not confuse the user in the case they don't have to scroll to the end.
¿Is this a reasonable approach? ¿Are there some reasons why not?