List of replacement tokens? Where can I find a list of the available tokens, so I can write things like {{ node.title }} in my templates?

The documentation says the best way to find a list of them is to use this: https://www.drupal.org/docs/8/modules/d8-rules-essentials/data-selection

Can anyone provide something more useful?
Those are variables, not tokens. They're arbitrary, and can/will change depending on what template you're in, what modules/themes you have installed, and how you have them configured. 

The easiest way to see what variables you have available in context is to use the dump() method:

{{ dump() }}


See Discovering and Inspecting Variables in Twig Templates for full details.