I am searching for an Markdown Editor, with a similar Live-Preview feature to Obsidian. In particular, I do not want to split the view into source and preview, but have the preview as the main window and only switch to source code for the line/block I am currently editing.
Nextcloud uses a similar feature for their in-browser editor, but I need an offline variant.
I use zettlr -- it's pretty good! The only issues I've run into are with the table editor, and with occasional lag on large documents; the latter just comes with the territory on an Electron app. I know Nathan's working on both, though.
QOwnNotes (https://github.com/pbek/QOwnNotes) may be an option as it is pure Markdown and need not have both the code and preview windows open. I used it before moving to Obsidian. It has some options to customise its window views, but it is a long time since I used it, so not sure if it has that block mode you want. Logseq I seem to recall worked with blocks as it is an Outliner that does save in Markdown format, but I did not like that the outline blocks added characters to the file format that slightly broke compatibility with standard Markdown formats. But blocks was Logseq's strength.
Joplin has this functionality, although I don’t often use it since I prefer to type directly into the Markdown editor. Whatever you choose, be sure that you’re comfortable with the security and privacy implications of it.
https://github.com/TriliumNext/Notes is a fork that appears to be actively developed. Found it near the end of the issue linked from the maintenance notice.