Or you can also place pureref somewhere else. Or there is a better reference image plugin for you which makes the reference image into a docker. GitHub - antoine-roux/krita-plugin-reference: A temporary Reference Docker for Krita 4.0.0
This will make it work like the reference image docker Krita used to have in older version. it will not overlap or hinder the canvas.
P.S. Also there is an open source alternative to pureref by our very own @Rebecca you can read more about it here - BeeRef - Open Source Reference Image Viewer