Handling note titles
First, let me say that Zettlr is a very well thought software and it really shows that a lot of effort has been put for it to support a sane workflow. I have some comments about the use of note titles while using Zettlr for Zettelkasten. Of course workflows are always somewhat idiosyncratic, but maybe my comments and preferences resonate with more users.
I guess most people who follow a Zettelkasten method use some kind of title for each note, although this is not strictly necessary. Based on what I have seen, it's common for people to include the title in the name of the file (such as ID_TITLE.md or even TITLE.md, as shown on Zettlr's example screenshots). I don't follow this aproach and prefer to have filenames as ID.md, which is the standard way Zettlr creates new files (I already did this before using Zettlr). I believe titles don't have to be fixed as IDs are.
In practice, most note titles will never change, but, because they are most useful as mnemonics, sometimes it makes sense to tweak a title to better reflect how the note fits in the ever changing network. After all, the unexpected connections and organic growth are core to Zettelkasten. Maybe the note became part of a sequence and it's now useful to add a number to the title, maybe you realize the title was too broad after reading and writing more, maybe you clarified an idea and the original title was a bit misleading. In my experience, this may happen on the same day, within a few weeks or several months after you write a note. So it doesn't make sense to "hardcode" the title in the filename. Also, from a programming point of view, it's useful to have basefilename = ID.
The main problem this option creates is that notes are more opaque on a cursory look. That is, because titles are metadata (such as tags), the list of files doesn't tell you much. So this leads me to how I think Zetllr can better serve this kind of approach. Some are derived from months of tweaking a personal Sublime Text plugin, which I still use (currently alternating between it and Zettlr).
First, titles could be optionally defined as metadata. The user could specify a regex to find it, just like we do with IDs. For example, I use a YAML frontmatter, so "title: (.*)" would do it. But I know that a lot of people define the title as the first level 1 header, for example. So to search or not for a title and how to do it should be up to the user.
If a title is defined/found, it should be shown on the sidebar. Actually, if the user chose to use titles as metadata, I think it would make sense for them to stand out. My preference would be to have something like "ID - TITLE" where the filename is currently shown.
Titles should be shown in the note list Zettlr shows when you type "[[". This should work in a similar manner to the citations panel: enough information is shown for you to find what you want if you vaguely remember the title (again, something like "ID - TITLE") and then the ID is inserted once you press Enter. Currently, if you don't include a title in the filename, the list shown after "[[" is not very useful and you have to resort to the "Find in directory" search box, likely click through a few results to check title/content, then copy the ID and return to the note you were writing to insert the link. By the way, as I guess someone pointed in GitHub, another problem with the current implementation of these panels is that hitting space breaks the search, so you can't search for more than one word. One thing I like about about my Sublime Text plugin is that "[[" opens a quick panel where I can fuzzy search a note by its title (ESC closes the panel without inserting anything, Enter inserts the selected note's ID). It makes linking notes incredibly fast if I vaguely know what's in the title. (The heavy lifting is done by Sublime, the plugin only supplies the list and gets the selected key).
Now extending this a little bit: a similar panel could be used to open notes. A dedicated shortcut (such as ctrl/command+alt+o) would open a list with "ID - TITLE" for you to search through, and Enter would open the selected note. Again, this is how I do with my Sublime plugin. For people using Zettlr for Zettelkasten, I guess that when they want to open a file it's usually a note in the current directory. Currently, if the title is not in the filename, to open a note you have to search, click through results (who remebers IDs?) etc, even if you remember the title exactly.
I guess that's it. Of course, please see these as general suggestions and not specific requests. That's why I thought posting here would be better that opening an issue.