In the examples in the Dyalog chm help file on drawing simple lines in a form, I drilled down into all of the various options you can place on a Form window creation and could not find a way to turn off the auto-scaling. That is, when I resize the Form, I don't want any object drawn within it to rescale their respective sizes in relation to the the new window size.
'F' ⎕WC 'Form' 'Drawing Lines' ('Size' 25 50) ('Coord' 'Pixel')
'F.Line' ⎕WC 'Poly' ((10 90)(5 60))