So I started a save with angel-bobs and a long list of other mods, but after a few hours I saw that there were going to be ore patches in my way. So I found that this mod was around and installed it, however, it doesn't seem to be something I can access in this playthrough. There is no listed research or recipe for creating the ore eraser. Have I missed something or does this mod not work of not installed before the map is initially played on?

You'll find the tool for the eraser in the bottom right toolbar, click the 3 small dots to expand it.

Added "How to" tooltip on Ore Eraser shortcut.