You may have found that creating Markdown tables is made more difficult by Mac OS X's default "smart dash" functionality. With this, any "---" is automatically replaced with an em dash "—". To work around this, you can uncheck "Use smart quotes and dashes" in System Preferences > Keyboard > Text. However, doing so will also disable smart quotes; if you wish to continue to have smart quotes, you can add a replacement text rule. Add "---" in the Replace column and "---" in the With column.
In order for footnotes to work correctly, include an extra line in between each footnote at the bottom of your document. See the following:
Some long sentence. [^footnote]
[^footnote]: Test, [Link](https://google.com).