Is it possible to customise (add, delete, change) the "Snooze until..." times in Google Inbox?
You can change the definitions for Morning, Afternoon, and Evening.
Open the "hamburger" menu and scroll all the way to the bottom. Click "Settings".
Choose the "Snooze" tab.
Change the times to what you want.
Unfortunately, you can't change "Later today", "Tomorrow", or "Next week", except insofar as "Later today" is whatever time (Morning, Afternoon, Evening) is coming up next, "Tomorrow" is your Morning time the next day, and "Next week" is the Morning time a week from now.
If that's a feature that you think Inbox needs, you should use the "Feedback" tool to let Google know.