Please note that the use of mods (e.g. Rebirth Workshop items, AKA "Extensions") or save game edits can break games either of themselves, after future game updates, or via conflict with other mods. Consequently, Egosoft are nor generally able to support modded/save-game editted games (see here for further details).
UI Modding support can be found at the modding homepage here.
Items are preceded by the Rebirth version they where either most recently adjusted or added with.
Mods are generally added to the Extensions in the game's route directory ( e.g. C:\SteamLibrary\SteamApps\common\X Rebirth\extensions ).
1.30: Mods can be subscribed to via the Steam Workshop.
Mods can also be found on the Nexus website.
An up-to-date list of many mods, and their status, can be found Egosoft's X Rebirth - Scripts and Modding forum here.
3.53: Loading order of mods (AKA "Extension ") can follow defined dependencies.
Save Game Editing Tricks:
http://forum.egosoft.com/viewtopic.php?t=377686