Thanks for clarify you query and sorry for the delayed response.
Unfortunately, I do not have answer for this question but hopefully our community people will able to help on this.
As per my understand, there is no options to delete or remove the standard templates workspace from Adobe Analytics (I have tired on my own). May be our Adobe team will consider this query and organize it near future.
The "Sample Project" is a default one every new user are able to see this templates in the Workspace category. However, there is no any possible way to delete the sample project instead you can create any custom workspace on your own then the standard templates will be hide default from the workspace.