Can we create Subfolder within Parent folder in Infromatica

No, we cannot create subfolder inside the main folder in Informatica. 

When one parent folder is created we will have mappings ,mapplets,source ,targets and transformation folders are created .Inside this folder we cannot create anyother folder.Else we need to make seperate folder under the same repository using repoitory manager and then make them as shortcut and use in the folder containing the mappings

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