Filters: duplicate

I have created a filter and now I want to duplicate it and then tweak the new filter. I’m not seeing any way to duplicate however.

… I think I’m missing the command as it’s hard to believe there’s no way to duplicate a filter. That would be like software-Sisyphus where one always needs to start at Step 0 instead of taking advantage of previous work done by a previous filter and tweaking it.

Can anyone let me know how to duplicate? Or if, in fact, it’s not possible?