Oh, ok ! I didn't knew about Tasks and that you were talking about that.
It seems you can't trigger Tasks on save by default, but this extension might do it
https://marketplace.visualstudio.com/items?itemName=Gruntfuggly.triggertaskonsave
I will look into it tomorow, when I can, if it works, I'll answer you on my request on Github to provide a way to do it, for other if needed, until you add it in Dendron ( 😉 )