This isn't really a feature request or a bug, but something that could be adjusted is the area that we need to click for the screenshot editing tools to work. I would normally expect that clicking anywhere near the icon would select it, any clicks in the black box being a hypothetical "click box," which is how tools work in Preview, but that's not the case here. (The red dots are examples of clicks that will not select the tool, greens dots are clicks that would.) So you have to click exactly on the icon itself or else it won't select it, and it's just a bit annoying to have to take that much care and precision with the mouse cursor to select a tool - often takes 2-3 tries to actually manage to hit directly on the tool's small icon.
Unfortunately I can not influence this as I'm using the standard, Apple provided image editor . It doesn't come with any customization options.