I would like to invoke the Mark Project as Current in my custom Update
How should I do it?
I guess project level properties not exist now. But you can create it by yourself. Create a ApplicationComponent named like, 'MY_PROJECT_MANAGER' or etc.
In any place if you need to get or set current project use:
MyProjectManager mpm = (MyProjectManager)Application.getComponent(MyProjectManager.class);
Project current = mpm.getActive();
This just an example, i think idea is simple to understand
PS. This practic i used in CurrentProjectComponent, but i misstake in source of "current project" and now this solution is depricated (http://www.intellij.org/twiki/bin/view/Main/CurrentProjectComponent). I use wrong algorithm for marking "active" project - i used ProjectManagerListener for this.
But for you target this solution is working correctly.