Looking for Storyboard Software

Mine are similar to yours, Daniel. A few differences but similar concept in row based capture of segments within a single element of a presentation or activity.

I like to have everything matched up side by side. I never use more than 2 columns to keep things simple and (mostly) readable. I add notes / remarks in [brackets]. If these are something I want to suppress from a reviewer, I'll add a style to my stylesheet and make them small and white to match the background. That way I can make them all bigger and dark when it's ready to send to the next stage (developer, if that's where it goes next). I usually develop my own stuff so I don't need to make a heap of notes to explain myself to myself I went crazy with the brackets, more than I normally would. This makes things a little less readable than I would expect.

There are a couple of advance organizers I like to add to the board as well. This can help avoid the need to add complex representations within the boards themselves. 

See the attached for an example of my style. This has been honed and adjusted for about 15 years. Simple is what I've found works best for all (and best for me). Many storyboard formats are just too complicated and hard to review.