At the start of my turn in Game #98188650 on Tokyo, on a few different turns, I want to do neither Silos nor Crafter's Guild. The correct way to do this is to click "Silos" and do nothing, and then the option to do nothing for Crafter's Guild appears. If I instead click Crafter's Guild first, there's no way to do nothing.
Abilities are color coded: Green outline: mandatory, white outline: optional
(https://i.imgur.com/Fj7eETW.png)
That's why there is no "continue"-button in this picture. At some point, you have to do the mandatory Silos effect. If you do it, you can discard 0 Coppers, which makes it quasi-optional and so the distinction to Crafter's Guild is only formal.