Right - you keep the shared code in its own overlay named
MyAwesomeReusableCode. Edit the
Skookum-project.ini file to reflect the newly added overlay. If you re-use it across projects you probably want to place it right between
Project-Generated-BP (so higher than engine functionality but lower than project functionality).
You can keep the files in just one project and link from other projects to it, or keep it in each project and set up a branch in your revision control that allows you to merge across.
You should not have to create files or folders in it, as the IDE will create those automagically once you add routines to that overlay.