This answer starts with what a workspace is. A workspace contains code from a github repository and any changes you've made to that code in the Leap IDE. Many workspaces can be created for the same repository, so in this case they would all share the same files and functions from that repository. If you make changes in one workspace and want to pull the changes into another, you have to push the changes to github and then pull them into your other workspace through git. You can only do this when the workspaces share the same github repository.
If you create workspaces for two different repositories you cannot share code between them. In this case, you need to use git to cherry pick a commit from one repository into the other.