Nowadays, once Creo VIew opened a file, then this file is always being using, can't be deleted. It's better to add a close file or clean memory function in Creo View. Thanks!
I would suggest putting this in the ideas section for others to vote on in the community and gauge whether or not this is a feature that others see as valuable.
You can submit it either to the Creo Ideas site (if you feel this is more applicable to standalone use of the tool):
or the Windchill Ideas site (if you feel this is more applicable to usage in conjunction with Windchill):
We monitor both of them for ideas related to Creo View.
Thanks again for your feedback!