The Folder Tools group in the Home tab contains controls for searching & navigating folders
The icons, from left to right
1. - Search icon - read more about searching here
2. - Open current folder in grid - opens the menu below:
Here you can choose images from the currently highlighted folder in the slide browser to open into your current grid, or make a new grid.
3. - Previous folder - selects and opens the previous folder
4. - Next folder - selects and opens the next folder
5. - Previous file - opens previous image in folder
6. - Next file - opens next image in folder