When speeding up, offer option to mute audio only for the part that is being sped up.
You can do that by adding MUTE Filter to the clip you are working on. (You May or may not have known that.) Yes an extra step, so would coding in an extra button you could press to have that option.
You can do this already in Shotcut. Go to the part where you are speeding up the clip and add the Mute filter to it. If you are using Time Remap then go to the sped up section and use the Mute filter only on that section by using filter trimming: