Normally you can right click on a new image, and give it a low/medium/high stretch. This works if I am using just my Windows 10 laptop.
I now use an external monitor attached to my laptop with “extended desktop”. Typically I have the SGP main window on my laptop, and the Sequencer window up on the external monitor. With this setup, when I right click the image and move the mouse over to “autostretch-medium” (or any other stretch option), I get rapidly flashing “mouse-over help” popping up and disappearing. I have to try to do the stretch 5-6 times before it takes.
If I drag the sequencer window over to my laptop screen, then the autostretch works as expected.
Related question: where do you set the default stretch for new images? I saw that setup once, but can’t remember where it was.