Just put a Text or Boris Title 3D wherever you want a watermark. Reduce the Opacity to control how visible it is.
If you need a watermark filter, here's a workaround:
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www.lafcpug.org]
I wouldn't use this method unless you absolutely need it on your master clips in the Browser. Filters are a lot more fussy to remove if you're using other filters (eg. Color Corrector, Flop) in your edit. If you do it as a text layer on top, you can turn it on or off with just one command (CONTROL-B -- Clip Enable/Disable).
www.derekmok.com