Okay, if I understand what you're saying, though I'm not exactly sure what you mean by browse, for the Movies and TV series things all you have to do is press the white button when in the video section and go to Add Source. There, you can add folders either locally on the xbox, or folders on a network, and you can name it whatever you want. Just do one of those for your tv series and one for your movies. For the scripts, you'll have to add a couple buttons on the left under where it says stack and view and sort by and all that stuff. This can be kind of tedious, because you'll need to do it for all the different view types...or maybe that's just a problem in the music xmls come to think of it. Anyway, you could probably figure it out yourself. Just look for the xml talking about the Stack button or whatever happens to be the bottom button in the view you're editing, and just copy and paste that right below it and then change the label to YouTube or whatever and change the action to <onclick>XBMC.RunScript(Q:/scripts/YouTube/YouTube.py)</onclick> or whereverwhatever your script is....You'll also have to change the ID number to something not already being used on the page, and change the onup number to match the ID of the button above it, and change the ondown button to match the id number of the button below it, or if its on the bottom, the id number of the button on top of the list. Also, you'll have to change the ondown of the button directly above the buttons you added, and change the onup button of the button below them lol. Oh, you'll also have to change the Y coordinates to be lower. you can try to figure this out by seeing how far apart the buttons above it are from eachother, and then do the same. So, i guess its more complicated than i was thinking...But, if you take the time to look it over, you should be able to figure it out, thats how I figured stuff out.
I just checked, and there are like 6 xml files you'll have to edit...They're named MyVideo.xml, MyVideoActors.xml, MyVideoGenre.xml, and so on, and they're found in the PAL folder. If you have a widescreen tv, they're might be some additional files you need to edit in 16x9 folder, but i'm not sure.
OH, just ocurred to me. I think you'll have to use a different overlay or whatever, depending on how far down the screen you are. You could try looking at a button in another window that's the same distance down the screen and that should be the same one.
So, i'm pretty sure you're just as clueless now as when i started typing this. But oh well. I might suggest you wait until MC360 v1.0 comes out so that you don't have to do this twice. It should be out soon...