Here is the newest (And Best) editor I just found, it needs Java to run, there is a link in the files download page on NMS Mods... When I saw it I was amazed, Radaxim seemed to drop off the planet and not update his editor... so I'm glad someone else did this mod..
Java 8 Link
For java, download the Offline version to run other programs outside of the browser..
Be careful w/ this editor I put too many items in the inventory and the game couldn't load them all, also Do Not move the default objects to the tech inventory like life support, jetpack, same goes for thrusters on the ships, seems to glitch it out.
Yea, the maximum displayable slots is 48. However you can give your ship more than that, and just sell or transfer items to and from it with the hotkeys.
I have 48 slots on my Exo suit, 42 in in technology, and another 48 in cargo. In Cargo I can have stacks of 5000 and 50 products.
My Muiltitool has 96 slots, my Ship has 96 and another 96 in Tech. Ship stacks are 5000 and 50 again.
My Freighter has 48 (only because once items go past the maximum displayable slots, 48, you can't get to them at all.) Freighter stacks are 50000 and 1000.
And each Storage container has 48 slots. With stacks of 10000 and 100.
All thanks to the Save editor.