The Atelier/Eclipse equivalent for jumping to a class/routine/macro referenced in the code you are looking at is F3 (or Open Declaration in the right-click context menu):
I don't know of an exact Eclipse equivalent for Studio's bookmarks. An Eclipse bookmark can be set on the line your cursor is at by going to Edit > Add Bookmark. Then you can open the Bookmarks View (Window > Show View > Bookmarks) to see a list of your bookmarks and double-click them to navigate to that line in the code:
The go to tag+offset feature is still in development for Atelier. It is a very high priority and should be coming in an upcoming version soon.
Here are another couple of keyboard shortcuts that I often use for Eclipse/Atelier navigation:
Ctrl+O (or cmd+O on a Mac) shows Atelier's Quick Outline, where you can see a list of members for a given class/routine. Hitting ctrl/cmd+O again shows the inherited members. You can start typing in this view to narrow down the members listed:
I also use Eclipse's go back and forward navigation commands to jump back and forth as I'm viewing/editing code. To go back you can use Navigate > Back, ctrl+[ on Windows or cmd+[ on Mac. To go forward it's Navigate > Forward, ctrl+] or cmd+].
Ctrl+Shift+R and Ctrl+Shift+T (again, cmd instead of ctrl on a Mac) can be used to open a resource or an Atelier class/routine, respectively, that exists in a local project. The "Open Atelier Class/Routine" dialog (Ctrl+Shift+T) will show server-side files in an upcoming version of Atelier.
There is also a page in the documentation on Atelier equivalents for Studio actions here.