Filter to ignore files with a certain extension

Is it possible to create a filter that will check when uploading and not upload files with a certain extension? I'd like create a filter, for example, that ignores Thumbs.db files.

Okay, so it seems you can't set the Overwrite to ask for Queued transfers. I switched to Direct transfers for this reason. But then you can't set the number of workers and the filters don't work for Direct transfers