Thanks for the reply Victoria. I just wanted to report that I did find a fix for this that did not involve changing the resolution on my display. The fix involved changing the high DPI setting for MLO as follows:
1. Right click on the MLO launch icon (either on the desktop or in the start menu) and select
Properties (at the bottom)
2 2. In the Properties window go to the Compatibility tab and select “Change high
DPI settings” near the bottom
3. Enable "Override high DPI scaling behavior" and select "System (Enhanced)" from the drop-down menu
Checkboxes in MLO should now appear normal size!
One other comment for those who may not be aware, but changing the display resolution is not the same as changing the display scaling in Windows 10 (right-click on the desk top > Display settings > Advanced scale settings). If you change the resolution on a 4k (3840x2160) display to 1920x1080, Windows will reduce the number of pixels used to render text and images by 1/4 (1/2 in the horizontal direction x 1/2 in the vertical). So although text and images will look twice as larger, they will not look as smooth or crisp. On the hand, if you keep the resolution at 3840x2160 and scale the display by 200%, text and images will look twice as large and look smoother and crisper because twice as many pixels are being used to form each letter or image. I have a 24", 4k display, and text looks almost like it's from a typewriter (no pixelation whatsoever). The only issue with this is that some applications, like MLO, don't handle the scaling properly. Fortunately, the above has fixed this for all my problem apps.
Anyway, hope this helps!
Pat