I'm not sure how widespread this is throughout the system, but I expect it shows up all over the place. If one attempts to post, say, a Purchase Order, and does not include the External Document Number, appropriately, an error message is displayed, explaining the problem at hand. There are so many problems with how this is done in Business Central compared to classic NAV.

1. Consider the fact that you had the PO open when this occurs. A new window on top of that PO shows up and covers the PO up. Depending on your screen, this error message could easily obscure the entire PO, including the field in question (External Document No. in this instance).
2. The amount of whitespace on the pop up window is excessive like it is everywhere else in this app. Never enough room for the fields needed to get work done. This is coupled with the fact that the pop up window maxes out at 970 pixels wide, no matter how wide of a window you're using. This width literally does not even hold the description of the error message! You can move the pop up to wide layout so you can see all of the text in the Description field, but that's yet another click, and that guarantees you obscure the PO in the background.
3. Then, you click the hyperlink that appears on the Description to take you to the record, and it opens up the PO, which is already open underneath, right on top of the error message. Not only that, it does it in Read Only mode, which, at our company, we have completely eliminated because you can't get any work done on a PO in read only mode.

So now you have a PO you were working on, an error window on top of it, then the same freaking PO in read only mode on top of that. Close down two windows and you're back to your original PO. Hopefully, you remembered which field you're missing!

The UI has never been worse for this product. The U has been dropped from UI as far as I am concerned.