I would suggest moving steps and related variables across projects with simple drop down. Similar to the way machine can be moved across environments.

In our environment we add new steps and variables in a temporary project so as existing projects are not broken for the new steps. Once the development and testing is completed for the new step and underlying code is merged with baseline we move the steps from temporary project to one of the existing projects. This process is cumborsome where we have to create a new step in the destination project and copy all the settings and variables across.

Once done we delete the step from temporary project but doing this sometimes results in differences in step setup which we want to avoid.