If you use sliders in a project that also needs to recognize inputs from the keyboard, it causes a problem. Once you use the slider, the "focus" remains on it until you click somewhere off the slider. (see https://scratch.mit.edu/projects/1078453466) This project takes the focus off the slider by hiding/showing it, but makes the slider a little harder to use.
Thanks to @papipupepappa for the hide/show method of taking the focus off a slider. From his project: https://scratch.mit.edu/projects/1067880803 Update - Oct.9 - moved the slider-change detection into a custom block.