I think we should invent words, because a dictionary is only a collection of words in use by human beings.
There's all sorts of kinds of non-dictionary words. And you can argue the "right to make them" because the structure that permits new words to be made is inherent in the English language
One is the (classic German) move of putting two words (or more) together to create a new word that is more than the sum of its parts. One of my favourites is "whirlwinged". A version of that is to take a dual word and replace one of its components such as shadowfall.
There's all sorts of things like turning nouns into verbs (the caravan rivered slowly through the valley), verbs into nouns (He could see she was a dier), and all sorts of variations on the topic. Using adjectives for nouns is also fun. The green extended to the far horizon. This move of using a word in a different version of itself is called transderivational morphology and that's a word I really like to drop into conversations once in a while - LOL!
Structurally, the precedence for things like, she was sung, exists in the fact that you can also both hang and be hung - the structure of language doesn't care for either content or meaning, nor even for what is in the dictionary. It allows all sorts to be done with it - you just have to be brave enough to do it!
And stand up for yourself if or should I say, WHEN proofreaders and editors go absolutely ballistic
Silvia