Current interface only allows for individual "click" selection of fields to add to a select clause which is extremely time consuming, without any way to reorder field selections outside of deselecting and reselecting fields. This is a mind-frustrating experience, that would be easily mitigated by exposing the ability to directly manipulate the SELECT clause via a pop-up window or other dialog/interface.
PLEASE consider this enablement, as outside of this gap, the designer experience is quite rich and reasonable / fit for purpose. The only other "low hanging fruit" I might add is the ability to SEARCH for fields (both business and technical), which right now in complex joins with multiple tables, could be a challenge for customers less familiar with the fields available. While I am on this topic, the data dictionary download, if it were to include and expose the descriptions in a manner that was browsable, would be value add.
But I will stop now - SELECT CLAUSE is the scope we should focus on here. :-)