Stylus Studio is a suite of powerful XML and XSLT development tools from Progress Software Corporation. It is designed to help developers create XML applications faster, more accurately, and with greater ease. Stylus Studio provides a comprehensive range of features including XML and XSLT editors, an integrated debugger, an XSLT profiler, and a visual XML Schema Editor. It also supports XPath 2.0, XQuery, Web Services, and other XML technologies. It offers numerous features to help developers with the task of creating, maintaining and deploying XML-based applications. In addition, Stylus Studio also provides integration with popular databases and other data sources, allowing developers to easily access and work with XML data.
Discontinued Last release of 2008. See https://sourceforge.net/projects/xpontus/files/
It is so simple and is even better than the pencil.