In addition to those things mentioned by our friends above, to have these nice subcategories,
add the content "Parent Tags" of the <eXoDosSetup>\Data\Parents.xml file, to the <YourLaunchboxSetup>\Data\Parents.xml within LaunchBox tag after old parent tags that you already have,
<LaunchBox>
[Old Parent Tags]
[Content Here]
</LaunchBox>
here is the exodos Parents.xml content you need to copy,
<Parent>
<PlaylistId>1e87a075-0745-4083-84e5-ded997d31604</PlaylistId>
<ParentPlatformName>MS-DOS</ParentPlatformName>
</Parent>
<Parent>
<PlaylistId>68c56cfb-b801-4f43-8c84-701c81b53b8c</PlaylistId>
<ParentPlatformName>MS-DOS</ParentPlatformName>
</Parent>
<Parent>
<PlatformName>DOS Magazines</PlatformName>
</Parent>
<Parent>
<PlatformCategoryName>Computers</PlatformCategoryName>
</Parent>
<Parent>
<PlaylistId>a0e07e13-547d-4dd7-b82c-3185f157fb4c</PlaylistId>
<ParentPlatformName>MS-DOS</ParentPlatformName>
</Parent>
<Parent>
<PlaylistId>b6b61188-656d-4775-8fdf-1bb5dca02aa6</PlaylistId>
<ParentPlatformName>MS-DOS</ParentPlatformName>
</Parent>
<Parent>
<PlaylistId>4d77a375-ee49-4da4-8186-1155c5ecb278</PlaylistId>
<ParentPlatformName>MS-DOS</ParentPlatformName>
</Parent>
<Parent>
<PlaylistId>2f7300e9-b25f-4bfa-b6b1-6a3fc281f157</PlaylistId>
<ParentPlatformName>MS-DOS</ParentPlatformName>
</Parent>
<Parent>
<PlaylistId>e64fb51c-ff5d-4fbe-919c-aa2249d78117</PlaylistId>
<ParentPlatformName>MS-DOS</ParentPlatformName>
</Parent>
<Parent>
<PlatformName>MS-DOS</PlatformName>
<ParentPlatformCategoryName>Computers</ParentPlatformCategoryName>
</Parent>