In reading through #5272, @python-and-fiction pointed out you can customize the progress bar further by editing the source of renderables/bar.py. I wonder if there would be any interest in making some of these variables class attributes so the user can customize them? Apologies if this is already possible/documented some where, I'm still digging into the ProgressBar docs.

# Thick
half_bar_right = " " 
half_bar_left = " "
bar = "█"

# Battery-like
half_bar_right = " " 
half_bar_left = " "
bar = "|"