Idea Summary
One of the most confusing things is not being able to edit multiples application or pages at the same time within multiples tabs in the same web browser, as it just messes up the session values resulting in undesired errors.
Use Case
Being able to edit multiple apex applications or pages in apex.
Preferred Solution (Optional)
It would be nice just to clone the session when you open a new tab, allowing concurrent page or application development within the same browser. This would also apply to apex applications, as the users also want this feature.