I like Scaler but the “Playback Timings” part of it is a bit hard to grasp and it doesn’t feel as though it needs to be. Having “Duration” in terms of percentages is quite unhelpful when trying to scan out how chords might work together rhythmically.
A minor fix would for “Duration” to be a straightforward ‘number of beats’ option, probably in 1/16, 1/8, 1/4T, 1/1, 2/1, 4/1 format etc - like delay timings which DAW users are pretty familiar with.
Just to spell out an example - I just set up a very basic vi-I-IV-I pattern and tried to see how it might work in a four bar sequence that didn’t sound like a plod-plod-plod affair. I quickly got lost when I started trying to extend the pattern and tried to work out how to fit some chords in for half a bar, and maybe get a triplet feel into some parts. The quickest way to do it was to capture the midi then drag and drop into my DAW to take a look, then repeat until I had something that was the right length.
Even if you keep the percentages - and please don’t - there aren’t really enough options to making the playback section flexible enough to compose a sequence with an interesting rhythm. The limit of eight chord slots in a pattern is also pretty limiting, but I can see that would be quite hard to change without major redesign.
What I’d really like is for you to replace “Duration” with a DAW-like arrangement view where you can see the bars (which can be changed according to time signature settings) and how the chords fit into them, and drag and drop the box edges to change length visually.