1. Create menu which allow to clean "Most Popular/Last Used" palette group
2. Move button "Show only palette groups for which libraries are defined on the page" to the top of Palette View
3. Show message like "No \"Last Used/Most Popular\" items yet. Start using Palette to add items to this group." in "Most Popular/Last Used" palette group, if there are no items to show.
4. Show message like "No items found" in all palette group, if there are no items to show according to search pattern