Hyphens in a location modifier expression with a noun and past participle.
Generally, you need the hyphen only if the two or more words are functioning together as an adjective before the noun they’re describing.
When you connect words with the hyphen, you make it clear to readers that the words work together as a single unit of meaning.
For locational compound adjectives,
If the absence of a hyphen is NOT causing confusion then it is not a good compound location modifier.
A greater Toronto-based company. (confusion: Greater Toronto or Greater Company?).
So.
A Greater-Toronto-based company.
A green city-based company. (confusion: Is the company green or the city?).
So.
A green-city-based company.
But combining more than one location with hyphens does not make the compound modifier function like a single meaning. We can add more modifiers before a location, but can’t add more locations before it and combine it with hyphens to make it a single unit of meaning. Though one exception is in the public transport system, where we may connect two locations like this "A London-Delhi flight".