use this mod by Jean-Antoine d'Anglerais: https://steamcommunity.com/sharedfiles/filedetails/?id=3280853573

If that doesn't work: (this is the method i used)

(I recommend taking the game out of fullscreen to make it easier)

1. In-game, save your map and remember what save number it is.

2. In-game, create a separate save of a random world which is within the uploadable size limit.

3. In-game, open the save of the uploadable world. (you will use this world to trick the game into thinking you're uploading a regular-sized world)

4. In-game, go to the steam upload button, add a name, add a short description. Don't write the full description in-game since it may take several attempts for this to work. Write the rest of the description on steam.

5. Before you click upload, Go to the workshop upload folder at
C:\Users\[YOUR NAME]\AppData\LocalLow\mkarpenko\WorldBox\workshop_upload

6. Go to the saves folder at
C:\Users\[YOUR NAME]\AppData\LocalLow\mkarpenko\WorldBox\saves

Leave both folders open

7. In the saves folder, find the world you wish to upload, copy all the files of your world.

8. In game, quickly click upload world, and paste the world you wish to upload into the workshop_upload folder. You have to be very fast in order for it to work, so don't write a full description since it will reset each time.

I usually leave the "x files already exist" tab open and quickly click replace after clicking upload to make the job easier.

9. Once the world uploads, you can go to the steam workshop and edit the description.

10. If you want to upload a thumbnail, simply edit the "preview.png" file. It will change once pasted.

Thank you for the help it has been uploaded and I did give you credit for it.