Sometimes my Project list or Contacts looks empty, why is that?

Any window providing a search function will refresh if you place your cursor in the entry field and press "Enter" (Return key) on your keyboard. So for example, if you want to see a list of Contacts in the Toolbox, but the window is empty, just place your cursor in the entry field (next to the magnifying glass icon) and hit "Enter" to show search results, which will be all Contact entries if no search term is entered.