Left join doesn't support literal joins
This means that a left join requires an actual value for each join record. (This defeats the purpose and was an oversight on original setup).
There needs to be a way to join based on the fieldName of another table as well as supporting multiple on statements. I was able to do this kind of reference using the following code, however it was caught by the error check that forces a value.
const otherQuery = Query.from(otherTable).on([['OtherThing, 'MyId']])
const myList = Query.from(someTable).select(someTable + '.*, otherTable.something').leftJoin(otherQuery)
The use of the array double makes sense here and should be allowed.