Description

You can install add-ons directly from the Marketplace using the url parameter provided you know the download link. This describes how to get the download link.

Server Link

1. Go to the Marketplace listing for the add-on
2. Go to the Versions tab
3. Expand to see all versions
4. Hover over the version you want and copy the Download link

Cloud Link

This is a bit more difficult. 

1. Go to the Marketplace listing for the add-on
2. Go to the Versions tab
3. Expand to see all versions
4. Copy the URL - it will be something like: https://marketplace.atlassian.com/plugins/org.swift.confluence.cli/versions
5. Insert /download before plugins and remove the "s" at the end to get something like https://marketplace.atlassian.com/downloads/plugins/org.swift.confluence.cli/version
6. Find the current cloud build number - use your browser view page source to find the first text that starts with data-build="1000
7. Add just the number to the url to come up with something like: https://marketplace.atlassian.com/download/plugins/org.swift.confluence.cli/version/1000004