Dark mode is definitely on the short list of future todos... will probably get to it in the next 30 days.
On toggleable, that is interesting feedback. It is a bit different. I wonder what made you feel like it was a toggle... The clickable round circles is a bit like iOS calendar. So it shouldn't be hugely unfamiliar. I did try playing around with different button looks before. But I'll think about this problem... thank you for bringing it up :)
What columns would you not want to see? And may I ask why? So far the comments have been mostly an option to turn off Instagram and Twitter.