Folders in the nav bar to allow for organizing Favorites and Smart Rules would be immensely helpful. DT3 is a victim of its success - with lots of use these two areas become hard to manage. Folders are a “low tech” feature which could be of really notable help in making DT3 that much more useful day to day.
I’ve got 53 smart rules sitting in my sidebar. This is completely subjective, of course, but for me that number is too large to be “tidy”; I have clustered similar rules within the list, but it remains untidy. Of course, most of the time those rules are hidden. But that’s just like that one draw you bung stuff into but know one day you’ll have to tidy up.
I know this is an old question, but FWIW, I offer a simple way to at least get separators into the long list of smart rules: define an empty rule with a title containing characters that make a visual line. Here’s an example:
The gray color is the result of marking the rule “disabled”. I use the character “─” (Unicode U+2500, “box drawings light horizontal”) repeated multiple times to make the (fake) line that you see in the screenshot. Unlike using plain em-dash, repeated copies of this character look joined, giving you an uninterrupted line. There are some other variants in Unicode if you wanted to use different line styles for different sections.
It’s not as good as having folders in the list of smart rules, but it helps me contain the visual clutter in my DEVONthink a little bit. Perhaps it will help others here.