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What is a “virtual desktop?” What are “other instances?” Do you mean Vaults—as in a repository of .md notes?
If I understand this use case, there isn’t a global Quick Open feature (yet, although it’s a good idea, feel free to post in #feature-requests) but I created a macro to do this if you’re on macOS and have access to Alfred or Keyboard Maestro: Quick actions in Obsidian from anywhere using Alfred on macOS) -
Yes, see the Outline plugin in Preferences → Plugin.
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Yes, see Unlinked Mentions in any given note’s Backlinks pane.
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What does “context-based” mean? Obsidian has powerful search features with RegEx, but it does not offer a “Related Notes” plugin (yet). It’s a good idea though!
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You can fold bullets and headings in Edit mode; there’s no such feature when Previewing a note yet, but this’ll hopefully be the case when Obsidian gets a WYSIWYG mode.
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Yes, you can open as many editable panes as you’d like.
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What is a “grid-like style?” You can write custom HTML if you’d like, and you can embed most YouTube videos via iframes (e.g., copy and paste from Share → Embed feature on YouTube).
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Obsidian supports Mermaid, which offers something like this. See https://mermaid-js.github.io/mermaid/#/ for more.
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Yep, see the Graph View (and look forward to 0.8.3 for a more fluid experience with related notes).
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I don’t know if any app will ever be able to do this.

Maybe wait for Neuralink? (only half-kidding!)