The use of the progress bars for volume and brightness is done by external scripts in bash. You can find them in my repo under Scripts-AwesomeWM
For ex: I have an AMD Cpu, internal AMD Gpu and an NVIDIA RTX Gpu, I control my brightness with /sys/class/backlight/amdgpu_bl1 or amdgpu_bl0. Yours might be different, same goes for storage etc but you get the point.