Is there a new feature for substitution in tagging?

I have tried to add a tag “vsaddin” today. But it was not accepted. However, there was another a bit bulkier tag already in the list. Something “qt visual studio add-in”. I certainly did not introduce such a text, when typing the first time. Lateron I have tried to introduce vsaddin in addition, but it was not accepted at all. Also searching the tags with vsaddin did not provide results anymore. However, I am quite sure that it had been a tag in the past.