Is there a way or a plug-in to manipulate context menu, i.e. rearrange context menu items, remove/add new items, create sub-menus & drag there individual items etc.?
The context menus when you right-click files, or do you have different ones in mind?
Could you give a couple of examples of what you want to do?
As you mentioned, I mean the context menu when I right-click files. Example: when I right-click a picture I want all the standard items (convert/set as wallpaper) as well as every other externally added item (for example: resize picture) to be under a sub-menu (say picture handling). When I right-click a music file I, also, want every choice (play/add to media list/convert/media info etc) to be under another sub-menu (say music handling). I also want to move up or down some choices (for example have the 'send to'/'open with' in adjacent places) and add my own ones. In other words completely manipulate the context menus! If such a possibility doesn't exist, perhaps you should consider implementing it.
This explains a way to do that. Be warned that it takes a bit of effort if you want full control over where everything is: