Use the palette, Luke!
HAH! I'm going to use this one!! Indeed, before looking elsewhere or wondering if a particular feature exist, just open the command palette, (ctrl+shift+P) which is vscode's own 'minibuffer' ;) ... and start typing the most relevant about the feature you're thinking about.
For example, if you're wondering if a plugin is needed to preview md files, open an md file, and make sure your cursor focus is into it, (if coming from a Leo outline's, make sure it's external file is opened, not the body pane)... open the command palette and start typing 'preview'! tada!
Context sensitive shortcuts and commands
Reading your exchange also got me thinking I should point out a point about vscode you should be aware:
Vscode is context sensitive with its shortcuts. For example:
Having the focus in a 'Leo' panel (outline, body pane) will react on Leo's shortcuts :
[ctrl+minus] replace, [ctrl+plus] replaceThenFind
While having your cursor focus in a regular (non-leointeg) editor, or explorer view, terminal, etc...:
[ctrl+minus] zoom in, [ctrl+plus] zoom out
It is the case for many other shotcuts, obviously.
to change shortcuts, you guessed it, use the command palette (ctrl+shift+P), and start typing 'key'
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Félix