1. Select the top-left first cell in the sheet that has the green triangle indicating the error
2. Scroll to the last bottom-right cell that has the error. Hold Shift and select that last cell
3. Go back to that first cell, there will be a clickable icon to do something about the error
4. Click on it and then click "Ignore Error"

This will ignore all the errors in the selection you have. But you must start with the first error to get the pop-up to ignore them.