What's munching on my greenhouse plants?

The clean, shiny paths are the mark of snails or slugs (which are just snails with no visible shell).

Diotomaceous earth will help keep them away. A saucer of beer left on your tables (please don't waste GOOD beer! Use some of that LITE crap.) will kill them by drowning.

For the other, see: https://ibonsaiclub.forumotion.com/bonsai-pests-diseases-f9/rogues-gallery-with-a-few-heros-too-t528-15.htm

I did a check and found a nice fat slug adhered to the side of a plastic pot in my greenhouse near the damage area. How it got inside my well-sealed greenhouse is a mystery, though.