[quote=Eldarth]But are they available in the toolset (not GM mode)?
...and if they are placed using the toolset, when using GM mode are they possessable or selectable and perhaps manageable/editable/adjustable once selected in GM mode? [/quote

Yes. I have done this.

GMAddon1: Adds almost every single monster and NPC from the main campaign into GM mode, plus a few large custom maps to use in GM mode.