Is it possible to create a variable in a rule, and use it in another rule?

Is it possible to create a variable in a rule, and use it in another rule?

Well yes, but you imply that you want to pass data from one rule to another, and that's not really how Rules works. Each rule executes independently in response to an event, and you don't get to choose the order of execution. So it's really unclear to me what you're trying to do and why. Regardless, you can set data values in Rules, but you will have to think about your use case and decide where that data belongs - is it associated with a user, a node, the site itself, etc. This then becomes more of a site design question than a Rules question, because if you have a clear data model then the workflow issues become a lot clearer.

If you have specific questions, rather than a broad general question, then please provide some specifics of your problem in a new issue.