I have two script projects for a spreadsheet. One was a temp one for development testing. I want to delete the temp one. When I click on script editor it shows both projects, and I can select one, but there is no option for deleting.
Also when I open the project itself there is no delete option. I have seen other SO threads (such as this), but it seems the interface is changed since then.
Attached the screenshots. 
Script Editor File menu:
Make sure that you are the owner of the script.
I've tried to replicate your issue in other scripts which I don't own and it seems that I cannot see a Delete Project... option under File menu.
But with my owned script, there is a Delete Project... option. See screenshot.
Here's a reference post: How can I remove a project from a Google Spreadsheet?
UPDATE (based from OP's comment):
You must be the owner of the spreadsheet to show the Delete Project... option.
来源：https://stackoverflow.com/questions/44379143/google-spreadsheet-script-editor-delete-a-project