I was just burned by this. Query Editor needs an undo or at least an option to back out without saving the latest changes. I just lost a lot of changes while troubleshooting a bad step. I was hoping that closing the editor window without applying would open it back in the previous state. No luck. This hurts.
Can't believe there is no undo option. Accidentally delete a step (easy enough to click on the X by mistake) and you lose the step. If you can't remember what it was, you have to work out from something broken in the reports. If not an undo, then at least a close without saving option so you can go back to where you started the edit of the query.
If you accidentally press delete (or undo applied step) on anything before the last step, you get a warning and you can cancel the action. If you do the same on the last step....tough luck. Unbelievable. And there is no SAVE option either! You have to close and load the query and then save the spreadsheet, and then go back to query editor.... it bewilders me that you build something so great yet spectacularly bad at the same time.
Anyone who has worked in the Query Editor has at times edited a step or made another mistake, where you immediately reached for an Undo. Only to find in Power BI Query Editor that the Undo option does not exist 😞 This would come real handy and would accelerate the learning curve of users. Since they would be less afraid to click around or edit M in the Formula Bar. Please prioritize this feature in Power BI Query Editor!
Just getting started with Power BI and this is an absolute must. It is insane to me how you can have deleting a step be THIS easy (clicking the x) and have NO way to go back and UNDO that mistake. I just completed a data transformation step that took me 30 minutes and was treated like a single step. If I click that little x button, I will have to jump out of the app before it saves or I save. That's completely silly.