I don't think it actually works?

zoom-to-fit/height/width is not working on images whose natural size is less than the browser window size.

Does nothing on MacBook touchpad

Did not work at all for me on Manjaro even after browser restart. Am I right, you click an image, select view image in menu, and then you should be able to scroll to zoom and/or pan by draging? nothing worked for me.

Too fast zooming for macOS Trackpad...