Lua is supported in 1.31 and maps can be set to use JASS
or Lua as their language... but
not both. Scenario > Map Options > Script Langauge. You can only switch languages with that menu when the following are all true:
- There are no 'custom text' triggers in existence (commenting out the whole trigger doesn't bypass this).
- There is nothing in the map's Custom Text header (click the map name in the trigger list).
- There cannot be any custom script lines at all in any remaining GUI triggers; disabling them directly does not bypass this.
So if you're deep in a project this may be annoying to change. I have no idea what happens if you try to export trigger data when the map is JASS and then import it when the map is Lua.