I wondering is there any documentation available on how to develop custom extensions. I have couple of ideas but not sure where to start. I would appreciate if anyone could help.
The Help Center and Wiki have a section,
ThingWorx Extensibility, which contain links to documentation and sample code for developing server-side extensions and widgets.
Provided you're using 6.0, yes. You can navigate the Help Center directly from the platform.
[09. ThingWorx Extensibility | https://twc.thingworx.com/Thingworx/Runtime/index.html#master=ThingWorxCommunity&mashup=TWCWikiSearchResult&wiki=GeneralCommWiki50&entryID=102944]
The documentation contained in this Wiki is now available in the Help Center for ThingWorx. You can find information about developing extensions at http://support.ptc.com/cs/help/thingworx_hc/thingworx_6.0_hc/index.jspx?id=thingworx09&action=show.