@mattma Yes, one of the things I'm working towards adding is the "tabify" command, converting leading spaces to tabs.
There is a thread here on showing "invisibles" (visualizations of whitespace characters) only on highlight:
If you want to show invisibles full time, I use the following:
And in my personal stylesheet I have:
I use a dark UI and stylesheet, so you may need to adjust the coloring and opacity for your situation.