Obsidian

 I have been searching for a note taking/management tool for some time. From a book, I encountered Roam, which looks exactly what I need. After some research, I realized that is is a proprietary software using proprietary data storage format, and store all data on a remote cloud server. This, along with its not so modest price tag, raises a red flag. 

Then I discovered Obsidian, which is itself proprietary (as opposed to open source) but it works on local, plain text (including Markdown) files, which can be opened and modified by any text editors. For now, it looks really promising!