Good day! First of all, great work with kakoune; I've been a user of vim for three years and was quite fluent in it, but have abandoned it without regrets three hours after having learned about kakoune.
However, as a newcomer, I've spotted a number of problems that have significantly slowed down my transition, and so I intend to specify the issues I've experienced.
First and foremost, it's the lack any systematization in the list of commands, due to which I'm always lost when browsing it. For example, I've learned about the existence of :tmux-new-window only yesterday, which was two weeks after seeing kakoune for the first time.
Browsing of the available commands would be a lot easier if they were grouped somehow. While creating separate groups for "editing", "wrappers for external commands" etc. would slow down the access to common commands, I believe that grouping tmux-*, clang-*, iterm-*, jedi-*, go-* and others like that would only be beneficial.
For this, one could introduce the notion of a command mask that would group together the entries that match it. Let's say a mask clang exists. Then no command with clang in it would be in the list, only the group is shown. When there is clang in the prompt, the list of completions shows the entries in the group and not the mask.
The next problem is that it doesn't seem possible to scroll down the list of commands without <tab>. Given that, as per the aforementioned problem, there are lots of commands in the list, it makes browsing a chore. Even if bindings for scrolling exist, they're neither pageup and pagedown nor <c-f> and <c-b> and aren't specified anywhere I've looked.
There has been requests for a way to get a list of commands in the past, but I'm not sure where that sits in terms of coherence with the rest of the editor (should there be a command? a default option? something else?).
Lately some commands have been renamed to help discoverability using fuzzy matching, but unfortunately this is not a silver bullet and reading scripts in the rc directory remains the best way yet, albeit cumbersome for regular users.