Ahh yes it took me a while to get use to this. No offense to JFS developer, but you could try OpenFunScripter? It’s the one I prefer. It’s kinda like JFS but I found the rendering is faster frame-by-frame and also it has an undo/redo history function. Very helpful using the common controls of Ctrl+Z and Ctrl+Y. Check it out!
https://discuss.eroscripts.com/t/openfunscripter-another-scripting-tool-1-0-8-release/4457