thank you for your concern, @tox123! we already have been creating tag synonyms, merging tags, and setting tags for automatic removal, but as you said, there are too many of them unfortunately!
you may as well help us remove redundant tags by suggesting synonyms to them or by removing them form questions through edit suggestions!
I renamed the [gameoffifteen] tag to game-of-fifteen and merged the questions tagged [fifteen] into the renamed tag. A tag synonym for "fifteen" is not necessary because text completion will show users the correct tag to use.
The Help Center article Create new tags says:
When creating your new tag, bear in mind that tags ...
must be no longer than 35 characters
must use the character set a-z 0-9 + # - .
The percent sign is not among them, that's why it's not rendered.
Bear in mind that the same article says:
When should I create new tags?
Most common ...