ImGui won't work in a breakpoint, but on the other hand it's more or less designed to do what you want, in the sense that there is not a lot of ceremony require

ImGui won't work in a breakpoint, but on the other hand it's more or less designed to do what you want, in the sense that there is not a lot of ceremony required to create a slider to adjust a variable (unlike, say, Qt, where you to need to wire a few things). So if you can keep your program running, you can use Dear ImGui as a sort of custom debugger front end. Many people in the video game industry use it to do exactly that.