The https://github.com/iaronaraujo/Terasology/tree/record_replay_trial branch was updated with Persistence! It is now possible to record a game session, close the game, and then replay it as much as you want later! A recording library was also created, so if you want to check some replays, clone this branch, open it in IntelliJ and then execute the game using "TerasologyPC" configuration. Then, once the game opens, click on "Single Player" and then select a game to replay. Once the game is loaded, it takes some time for the replay to begin. It is also important to know that lag affects the replay, so it is possible for the events to not be replayed exactly as they were recorded.
If you want to do more than just watch some replays, you could record your own game. To do so, go to TerasologyEngine, line 179. There are three lines below this one, two should be commented and one should be activated. In order to play the game normally and to create new game worlds, make sure the NOT_ACTIVATED line is not commented. To make a recording, only the PREPARING_RECORD line should not be commented, then execute the game, select "single player" and then choose a game that was created previously. If you try to record a game that wasn't previously created, the recording won't work. Once the game starts, your actions will be recorded until you close the game or exit to the main menu. After a recording is done, you can see a new folder in the "recordings_library" folder, and you can replay this game session!