Showcase Brick Builds are only temporarily available until new ones replace them. You can find LEGO® Worlds Showcase Collection Pack 1, with all the 2017 showcase content for Free here:
https://steamhost.cn/app/816880/LEGO_Worlds_Showcase_Collection_Pack_1/
LEGO® Worlds Showcase Collection Pack 2, with all the 2018 showcase content for Free here:
https://steamhost.cn/app/1046500/LEGO_Worlds_Showcase_Collection_Pack_2/

If you experience issues with Collection Pack 2 you can use this save game backup to recover Showcase Brick Builds.

Both methods featured here were successfully tested on Title Update 3b with existing save games and on new game. Neither method should be able to cause damage to your save game even if you fail to follow the instructions correctly but this recovery method is not officially supported so use at your own risk, if something does go wrong you cannot rely on support from Tt Games or WB Games to provide a solution. If you're uncertain create a backup of your save data first.

What we are going to do is make LEGO Worlds act as if previous Brick Builds are currently available in the Showcase, this requires replacing the current selection of Brick Builds, so first make sure you've added brick builds currently available before proceeding. This does not permanently alter your Brick Build showcase, once the showcase is updated with a new Brick Build it will once again show the current selection or you can revert to the current Dashboard XML at any point by deleting the backup version and the game will download the latest.

Do note that the performance of the Showcase depends on your system specs, "Building Models" and "Grabbing Models" can take a fair while, especially for the very first model you grab after adding many Brick Builds, the following models you grab should be added faster. If you run into issues there you can try a different approach explained in 'Alternative method' below 'Instructions'.

• Quit LEGO Worlds
  
• Download this ZIP file http://s000.tinyupload.com/?file_id=02903294613926592644, it contains every Showcase Brick Build released in 2018.
  
• Copy all files except except DASHBOARD167.XML to this location, you can skip overwriting any files you already have.
  C:\Users\<USER-NAME>\AppData\Roaming\Warner Bros. Interactive Entertainment\LEGOWorlds\GUI3\ASSETS
  
• Then go to the LAYOUT directory and check the number on your newest DASHBOARD**.XML, rename it adding BACKUP to the file in case you want to revert, now copy the DASHBOARD.XML from the ZIP file to your LAYOUT directory and rename that file to include the latest number (e.g. DASHBOARD167.XML)
  C:\Users\<USER-NAME>\AppData\Roaming\Warner Bros. Interactive Entertainment\LEGOWorlds\GUI3\LAYOUT
  
• Launch LEGO Worlds
  
• Once on the Galaxy Map, click bottom left PUG-Z to show buttons and click Back
  
• The Showcase should now be showing all 2018 Brick Builds, click the Save Model [+] button for each Brick Build you wish to grab, do note dozens of models in in the showcase simultaneously can slow down this process.
  
• Done, the showcase builds can now be found in the Brick Build menu of the Discovery Tool and Free Build

Some systems may not cope well with making more than normal Brick Builds available in the showcase, this is likely due to memory capacity but even when models load the game may get stuck when grabbing them.

This method bypasses the showcase altogether and instead of relying on the files downloaded from the LEGO Worlds server uses the files from the models directory after being grabbed from the showcase. The reason for preferring to go through the Showcase to recover Brick Builds is that the game does not simply copy the asset files to your save game when grabbing a Brick Build in the showcase, it makes a modification to the files affecting what you are able to discover. This process could change in future updates, so its unknown what consequences bypassing may have.

WARNING, the 2 ZIP files associated with each method are NOT interchangeable.

• Quit LEGO Worlds
  
• Download this ZIP file http://s000.tinyupload.com/?file_id=09511247415351337272, it contains every Showcase Brick Build released in 2018.
  
• Extract the MODELS directory in the ZIP to this file path for save slot 1:
  C:\Users\<User-Name>\AppData\Roaming\Warner Bros. Interactive Entertainment\LEGOWorlds\SavedGames\CONTENT\S1-SYSGLOBAL\MODS
  You can skip overwriting any files you already have. Unzipping it there should place the .PNG icon files in \MODS\MODELS and the .SAV model files in the \MODS\MODELS\CACHE
  
  The file path for save slot 2:
  C:\Users\<User-Name>\AppData\Roaming\Warner Bros. Interactive Entertainment\LEGOWorlds\SavedGames\CONTENT\S2-SYSGLOBAL\MODS
  Save slot 3:
  C:\Users\<User-Name>\AppData\Roaming\Warner Bros. Interactive Entertainment\LEGOWorlds\SavedGames\CONTENT\S3-SYSGLOBAL\MODS
  Save slot 4:
  C:\Users\<User-Name>\AppData\Roaming\Warner Bros. Interactive Entertainment\LEGOWorlds\SavedGames\CONTENT\S4-SYSGLOBAL\MODS
  
• When done correctly your \MODS\MODELS\ directory will have new .PNG icons and \MODS\MODELS\CACHE will have new .SAV models.
  
• Launch LEGO Worlds, showcase models should now be in the Brick Build menu of the Discovery Tool and Free Build.