Remove filter from Html Form Web part

I've created a HTML form web part and connected it to a document library web part. It filters fine and as expected, but the only way I found to remove the filter is to reload the entire page. As I have several html form web parts on the page, filtering on different columns, that is a quite unsatisfactory method. Isn't there a value I can pass to the connected web part that just means "any". I've tried to send empty strings or '*' or even '[everyone]' (for the modified by column) but nothing works. Is there really no way?

Thanks!