A Polybar script that shows opened and minimized windows on your current display (if there's an active window it's marked by #). You can click on any window title to switch on that window (or expand minimized window).
Simple version:
Decorated version:
I recommend to look at repository Polywins, which is much more cool and configurable version of this taskbar.
xpropwmctrl
Comment 'Decorated version' block and uncomment 'Simple version' block to switch on simple version.
[module/polybar-windows]
type = custom/script
exec = polybar-windows.sh
format = <label>
label = %output%
label-padding = 1
interval = 1