In Lazarus, i haven't yet found a way to either get several editor tab sets or windows without producing an explosion of clutter, or in some other way to quickly go to an arbitrary file in a project.
I often keep 2 editor windows open, side by side, both almost from screen top to bottom. More than 2 would be clutter, yes, but so it would be with Delphi 7.
This is also why I prefer the undocked layout with separate windows. I get high editor windows and can keep helper windows like Messages and Call Stack partly behind them. The helper windows get focus only when I really need them. This layout utilizes best the available space.
In Lazarus the editor bookmarks are global for all files, not local for each file like in Delphi.
Thus jumping in code with bookmarks is handy. 10 marks is enough because it is quite the max to remember (for me). Often I don't pay attention which file gets a bookmark. I find an important place in code by jumping in it or by debugging. It can be in .pas file or .inc file, who cares. The bookmark will take me there later.
So, for me it works very well.