Intended as a replacement for Chisel's Merge extension, this plugin for Weland will copy most elements from one map to another. See README for installation and usage notes.
I didn't need this until recently, but it worked great. You could use this to work on a level in multiple sections. I use it to duplicate a level's geometry within the same level, for some experimental lua scripting.
Does not work for PC Weland.
PC Weland does not register any plugins.
May not be the plugin, may be Weland.