Is this modification possible.

[Goblin Wizard]

If you've found explosion_distance modifier you can see damage modifier right next to it. So what's the problem?

Two things:
1. If you want to be sure if something works or not you have to buy one from the shop right after you modified it. Modules in your inventory keep stats from the moment when you got them.
2. Visual explosion has nothing to do with real damage radius that you want to modify.