@nevil, I just meant those docs do a good job of explaining what the two different graphic query building modes are for, and what you can do in each of them.
The Simple mode was built to enable quick, interactive explorations and visualization of data for less experienced users or for quick-and-dirty queries. The Custom editor always displays the full graphical representation of any GUI-based query, and can be used to perform more advanced functions, like joining data, using the results of a saved question as starting data, writing out formulas for custom columns or metrics, or doing multi-step aggregating and filtering.
Our opinion of the old query builder was that it was too complicated for novice users, yet too underpowered and cramped for more advanced users. It was a constant struggle to figure out how to increase the power of it by introducing joins, multiple metrics, filter expressions, etc. without breaking the UI. Simultaneously, the old query builder didn’t always map to the mental models of novice users, who were coming from backgrounds using Google Sheets, AirTable, and the like.
Regarding the buttons below each step in the Custom question mode, those are the steps that are available to be inserted right after that existing step. The buttons are not always exactly the same because it does not always make sense or is not always possible for a particular step to happen after another step. This mode is meant to be viewed as a sequence of steps, top to bottom.
By the way, if your goal is to see data rapidly and then decide how to query/aggregate it afterwards, the Browse Data button in the nav is probably the fastest way, and is an answer to why it is a distinct action vs. asking a new question. You can click it to quickly see the contents of your databases, and clicking on a table will immediately show the raw data for it. It also defaults you into Simple query mode, from where you can then filter or aggregate the data, or click that editor button in the top-right to toggle into Custom mode if you’re trying to do something more advanced. Because the New Question and Browse Data actions are so common, we chose to not hide them under a submenu click.
@actionhank, sounds like you’re talking about in the Custom query builder how if you’ve displayed the preview of an intermediate step, if the step (like a filter step) changes, you have to click the Preview button again. This is a trade off as we have many users for whom even the preview queries could take a long time to run or be expensive operations, but I do understand where you’re coming from.