Hi J-P, please try the attached script, I think it should do the kind of batch processing you wanted.

There are instructions for installing a plug-in here. This script doesn't show any UI so it only has a .js file, not any .htm file.

Please note that the batch processing changes all the 3DM files in the given directory, any piece that is not in the world YZ plane will be deleted, and the 3DM file will be resaved in place so make sure you have backups of these files before processing them.

Before running it, use a text editor to change the directory name at the top of the script.

Hope it does what you were looking for!

- Michael