This is one of the most needed features for Toodledo in my opinion. I would prefer a tag cloud or list of previously used tags to pick from, but either way would be good. This would also be a huge help for the iPhone app.
I may be dreaming here, but it seems that Toodledo added this and did not mention it.
Can anyone else confirm that Tags now show a pull down list of existing tags based on what you type?
I'm afraid you are in fact dreaming. Firefox does this for you. The main problem is that your form history is erased with your other private data when you clear it. You can change that setting, but then you can never delete any form data that you have used anywhere from your history.