I have thousands of photos that have the filename embedded as a keyword. Obviously each image has it's own filename, so that particular keyword is only used once. Is there a batch way to remove the filename from each of these photos, either with Lightroom or with some 3rd party application? It would take a long time to go through thousands of photos individually removing that one tag.
I am not aware of a plug-in that can do this; you could write an SQL program to perform this task.
Presumably, all of the "filename" keywords follow a similar naming pattern, e.g. DSC03196, DSC03197, ... If so, you delete them relatively quickly within LR. In Library, go to the Keyword List panel on the right. Scroll to a group of keywords you want to delete. Click on the first keyword, then shift-click on the last keyword to select the entire group. Then click the "-" button:
This will delete the selected keywords from the keyword list and also remove them from the photos.