May I just re-direct you to this thread which I made a little while back: http://star-made.org/content/spawning-materials
Whilst the download link is not a mod or anything that will give you a creative mode, it does contain a program which you can run in conjunction with Starmade to aid in finding IDs and spawn the materials into the game. It is just a stop gap until something like a creative mode is either implemented.
If you find my download useful, please leave a comment on my thread.