I was playing with the new Notes 8.5 Mailtemplate today and found a new feature:

@WhichFolders

Its in a column in the "All Documents" view and showed the folder where the document was placed* in. To use it you need the Standard (Configuration) Client [8.5.0 or above] not the Basic one. I was also able to use a 8.0.2 Standard client to use this feature. Seamed this is a undocumented feature, I wasn´t able to find something in the Notes/Domino 8.5 Readme.

* A folder in Lotus Notes/Domino isn´t the same like in a OS (=Operation System). You can place a document into a folder, delete the Folder and the document will not be deleted. Or you can add one document to more then one folder. That means the folder remembered which documents are "in it".