I have multiple projects and each project has at least 2 stages. Some of the project stages can start in parallel while others start after one stage of the project ended. More, some projects depend on stages of other projects. Beside that, I have some processes that affect some of the projects and some stages of the projects are part of a common event. Now, how can I organize all this information efficiently to show both project stages and dependencies between projects?
You need to build an integrated master schedule. You need to pull in all your separate projects' schedules into one schedule and link them. You can link the work packages from different projects directly or you can create major and minor milestones within a sub project and link those, or a combination.
Based on Mark's comments below, I do need to add as part of my answer here that building and maintaining an IMS is not for the faint of heart. It requires capability and resource commitment and you need to have someone who knows what they're doing run it for you. A large IMS can become very complex quickly and subject to error. When that error surfaces, you will lose stakeholder confidence in the tool and that is very hard to get back. Not only this, but even when correct, your team members will accuse it of being incorrect when it begins to exhibit bad news. This is a lot of work but necessary work.