Makelangelo vertical plotter can hang on a window with these hooks. They pair perfectly with ULINE suction cups (https://www.uline.ca/Product/Detail/S-16142/Store-Supplies/Suction-Cups-with-Hooks-Medium). A padded chair foot at the bottom end is also helpful to reduce vibration noise in the glass.

Moisten the cups before applying to a window and they'll stay up for over a year. Tested many times over!

Tip: mark the circles of each cup on the glass with a Sharpie and use the plotter to draw the A2/A1 rectangles directly on the glass. Then when you put up a new paper you'll be perfectly centered. Also if you remove the machine and return, the marks will still be there. Sharpie marks can be removed with a window cleaner or rubbing alcohol.