I’ve seen this on creating different objects (tables, packages, views, etc.), and I’ve just seen it again on Materialized Views, I’m just not sure why it does it.
In the Object Navigator, click on Materialized Views, and then right-click and select Create. A dialog box will ask for a Name. It doesn’t matter what you type in there, because after you complete everything you need, and then click “apply changes to DB (ctrl-S)”, another dialog box will pop up and ask for the name again. It has the original name, and it’s easy enough to click OK, I’m just wondering if that is by design?