Obsidian Introduction (at least here)
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Obsidian.md is the software tool that I've used to implement my Life OS, FAKRA which I am presenting as Build YOUR Life Operating System. It is a Markdown editor and display tool but is expandable by plug-ins. This has generated a vibrant community of users (process) and developers (extended functionality).

The fact that Obsidian is based on markdown makes it an 'open' tool in that there are other editors/readers that can be used with the file. The files are stored locally, so you are not 'captured' by a provider, although the developers of Obsidian do offer extended services for synchronizing your files across devices and publishing your notes as a website.

Advanced Tables

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Calendar

Dataview

Emoji Toolbar

Homepage

Hotkeys for specific files

Kanban

MetaEdit

Natural Language Dates

Note Refactor

Pane Relief

Periodic Notes

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QuickAdd

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Sliding Panes (Andy's Mode)

Tag Wrangler

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Templater

Workspace Plus