Select a box and edit it

You can only use onLButtonDown() from within a Tool class instance.

Refer to the Ruby code examples for a Tool example.

You will likely have to write a picking tool that uses the Sketchup::Pickhelper and Sketchup::InputPoint classes.

Also, because a group is really a “special” kind of component instance, when you edit it with code, you are actually editing it’s definition’s entities collection.

Please post Ruby API questions in the Ruby API subcategory.

We will not write your code for you. You must at least try to write code, and then come and post questions for specific problems you encounter. (When you do, post in the correct category and post a the code snippet you are having problems with.)