Below is a start to get you going.
At first I thought I had to split it because some stupid error message:
The text that you have entered is too long (22316 characters). Please shorten it to 10000 characters long.
Then I found there is a stupid image limitation as well, so I moved everything to a MarkDown based gist.
You have included a total of 59 images in your message. The maximum number that you may include is 4. Please correct the problem and then continue again.
None of the artificial posting limitations are made clear upfront. Luckily this allows me to use a proper markdown instead of some vague buggy BB code knockoff implementation.
- you probably should extract this from your source code as I might have changed a few; at least I've added "Compare" to the toolbar
- that "Compare" change should be the default anyway, please submit that as a feature request.
- the dialog should show a legend of the keys (see below)
- defaults should minimise usage of keys only available on external keyboards (few Macs come with those anyway and few people have them)
- the list-view should be a few pixels higher as it doesn't fully show all lines. the list-view should be wider and the columns re-sized to fit all information properly (right now, some columns are wider than they should be and others narrower; just re-sizing the current columns would make it much better; see the jump in the columns near Folder Compare screenshots).
- there are way too many permutations (as for all kinds of views, the menu/toolbar/shortcut can be changed for all the commands common to any shared view). I think it's wise to discuss a more simple approach.
Since hardly any Mac keyboard nowadays should the symbols used in the Shortcut column, you should display a legend:
I've listed only the English layouts; international layouts are at [url]https://support.apple.com/en-us/HT201794[/url]
Below all the config settings for each view. It's a list of screenshot URLs per view that should be merged together.
--jeroen