I frequently work on multiple projects in parallel. For example, at the moment I have one project that is a wrapper around graphviz, another than is a DSL for probability expressions, and then an application project which is using these two as libraries. Each of these codebases live in their own repositories and have their own maven builds. They are separate IDEA prjects with their own top-level IDE windows.
While working on the application project, I sometimes find bugs or missing API in the library projects. So, I have to switch workspace to those, fix it, build and deploy, and then switch back. In the app project, if I click on a type from the library projects, it loads it up in the bytecode viewer and doesn't know about the source.
What I would like is proper support for project fedoration. So, in my app project, when I click on a type in a library project where I have the source, it offers to take me to that IDEA session in the other window. If I click on some 3rd party library, it would be great if there was an option (where the info is available) to check out the code for that library and load it up as another project.
Good support for multi-project development is lacking in all IDEs. Having it in IDEA would make my life easier.