From the secret guide:
https://support.omnigroup.com/documentation/omnifocus/mac/3.4/en/the-inspector/#dates
Scroll down to Supported Date Formats. Looks like it doesn’t like you writing out “in” or “two”. But +2w or even 2w seem to work. So does +2weeks.
For editing a task name, see under Preferences > General. You can choose either escape or or tab to begin editing. Command-return also works.
