To view your files in Markdown format, you need to download a dedicated
extension from the internet called "Markdown Viewer"...
Opera is based on the same engine as Chrome and natively supports Chrome
extensions, so you can download the extension from the Chrome Web Store
website.
Here are the exact steps:
1. Open the Opera browser.
2. Go to the
=> https://chromewebstore.google.com/detail/markdown-viewer/ckkdlimhmcjmikdlpkmbgfkaikojcbjk
page on the Chrome Web Store.
3. Click the Add button (or Add to Opera) in the top right corner.
4. Confirm the installation by clicking Add extension in the pop-up.
You must authorize Opera to read the files on your computer.
1. Click on the cube icon (Extensions) in the top right corner of the
Opera bar.
2. Click on Manage extensions (at the bottom of the drop-down menu).
3. Find the Markdown Viewer card.
4. Check the box Allow access to file URLs.
Take your .md file from your computer and drag it into an Opera tab.