In build mode, you will find two sections which were never previously included in the other instalments of the series - Featured and Storage. Both of them are designed to help you navigate your way through build mode.
In the "storage" tab, you will find all of the items that you have previously purchased and then removed. You cannot sell the items in this section. You will also find furniture and decorations that have disappeared when moving walls or removing entire furniture compositions in this very section.
In the "featured" tab the game will show you 4 items that it considers the most necessary and useful in your current situation. They change when you increase your experience level.