Well, all the built-in tokens are listed on the Settings/Printer G-code tab.
Most are fairly self-explanatory and very few are needed to generate great prints.
Only a couple may need explanation:
<MATL> this token is replaced in the generated G-code by the content of the upper left box on the Settings/Matl G-code tab
<TUNINGVAL> this token is replaced when the Wizards/Tuning Wizards is active and set to <TUNINGVAL> G-code token only. A good example of this is tuning for Linear Advance. Set [*]N Layers to 1 and in the N[*] Layers tab, enter
User-defined tokens can be created per material; you may find that every time you change extruder (material) that you need a material-specific setting not available elsewhere, so create your own token and add that token in the appropriate Printer G-code section.
Hope this helps.
Peter