I looked at the fix and setting the percent to 100% will not fix the problem. Messing with the percentage in Regedit, it appears the magic value is 93%. At 95%, I get the same window as shown in my original report, plus the toolbar across the top, but nothing else. At 93%, the toolbar shows, as well as the splitter appearing at the top of the window. At that point, I can use the splitter to resize the sections and see everything again.
The above image is what my Grep results window looked like after compiling version 1.3.17 and using it for a while in Delphi 10.4.1. After reading and trying suggestions in the discussion about the Grep window being blank and nothing working, I went into the GExpert's registry entries and discovered the value "ContextHeightPercent" was set to 125. Reducing the value under 100 fixed the problem. My guess is after checking the check box "Save context display (fixed) height", something caused the Context section to get set above 100% and from then on nothing would allow me to set it lower. I did not look at the code, but I would think it needs some logic to keep the context section from going over some value less than 100% to keep it from covering over all the other components.