Hi,
The data-entering forms for example Sales invoice form is too long, whereas when invoicing has to be pulled towards the left to enter every field on smaller screens like 600*800.
Here’s a thought that might help. Could you take all the various check boxes below the line items and collapse them? If something needs to be changed in that section then you can open the collapsed list and choose as necessary. For those invoices that generally don’t need to have changes made each time you’d save a lot of space on the Invoice (or other forms with the same growing list of options).