This may not be possible, but if I never ask I'll never find out for sure .

We like to create custom addresses for various  online uses, so that for example anything that that comes to lw-facebook is somehow from Facebook, etc. (It also helps spotting scams -- if I get something that pretends to be from eBay and it's not to the address I created just for eBay, I instantly know it's spam).

It would be nice to have, for example, all mail that comes to drw-{whatever} forward to my son's main address, everything to pjf-{whatever} forward to my husband's, etc. I tried creating a drw-*@silver-gateway.com forwarder, but a test email went to the catchall address instead of where I'd tried to direct it.

Is there a way to do this, or do I have to continue creating a separate forwarder for each variation we use?

Thanks!

You can do this using 'matches regex' in Main > Account Level Filters or I think it was just Mail Filters on the older cPanel.
Regex is short for Regular Expressions, a way to match strings in a more sophisticated way than simple wildcard characters. It's quite a big subject but there are plenty of resources out there that will help you create the right expression.