When using VSCode for markdown editing, you can have your attachments separated into their own folder like this:
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Go to your settings under “Markdown > Copy Files: Destination” and click “Add Item”.
Under “Item” enter **/*
and under “Value” enter assets/
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FYI: I’m using the extension called: Markdown All in One
https://marketplace.visualstudio.com/items?itemName=yzhang.markdown-all-in-one