Not yet. With Word Web App you can see WordArt that’s already in your doc, but to add more WordArt you need to open or edit the doc in the desktop version of Word.
If you have Word, click Edit Document > Edit in Word, or use the Open in Word command to open your document in Word.
Then follow the instructions in Insert WordArt.
When you save the document and reopen it in Word Web App, you’ll see the WordArt you added.
Tip: Word Web App works seamlessly with Word and other Office desktop programs, and we update it based on input like yours. For the latest feature announcements, visit the Office Web Apps blog.