JSON type is supported. Just type 'json' in the column type field by hand. Type selection popup contains only the most common used types.

We don't plan supporting enum and array types at this moment. But you can also type them manually in the column type field and they will appear correctly in generated SQL script.

Thanks for reporting this. We added this synonym as well as boolean.  BOOL is accessible from the column type picker, but if you type BOOLEAN in column type field it will also work.