Is there a keyboard shortcut / key modifier for adding links to the Reading List from Mail? You can hold ⌘ to open the link in the background, but that seems to be about it.
In Safari, you can ⇧-click links to add them to the Reading List. Does such a shortcut exist in Mail? I'm aware of the Add to Reading List command available in the context menu; I just find it more cumbersome than I'd like, especially for newsletters such as StackExchange's, which are essentially a collection of links.
Best Answer
You can use Keyboard Maestro with a macro such as this. The following macro will add the link to the Reading List if the link is clicked whilst holding control and alt. Holding control means it will be right-clicked anyway and typing the text means it will select the option from anywhere in the list.
If you have multiple services enabled, you will need to add a step to select the Services submenu.