If you click on Odd Grooves to the left (the libraries column), you will only see Odd Grooves files, and it's sub folders...
You can also choose to only show files that are in the currently selected folder (not its subfolders). Go to Grooves menu (top left of Grooves tab), un-select "Show MIDI Files from Subfolders"...
If you have non Toontrack MIDI folders, you can add them to the Grooves tab in Groove menu > "Add Linked Folder..."
