A sandbox is a subpage of your user page where you can experiment with editing. You can have multiple subpages if you like. Wikipedia has a more sophisticated version of this option that can reset to blank space easily, but this simpler option should work well for Theosophy Wiki.
To create a sandbox, key this format into the search box:
For example, if your user name is Santa Claus, key in
- User:Santa Claus/Sandbox
You may like to key in some placeholder text such as:
- This is a sandbox used for development of new articles and templates.
and save the page. You can use it to experiment with a new article and copy it into another Theosophy Wiki page whenever you are satisfied.
There is no way to keep your sandbox private at the moment, so bear in mind that it is visible to other editors. It would be a bit rude to explore another person's sandbox without asking, and even ruder to modify it.