It looks like that is the cockpit hatch used the older TIE fighter sets. The more rescent ones, like the Inquisitors prototype, have a new design one that looks great too!
I love the back end of this- I think that's the hardest part to recreate in LEGO. The next time I order bricks I think I'll do a similar thing to my Interceptor!
I have an LDD file of a similar one. I found it on a reddit thread a while ago, but it seems to have been deleted.https://www.dropbox.com/s/r6j5dtclqfk8gyc/Tantive%20v5.lxf?dl=0 Let me know if that works!