Is there a word for a subset of English specifically designed to be easily understood by non-native speakers?

Solution 1:

Basic English

or

World English,

with their different nuances, are the simplest terms that capture exactly what you are asking about.

Basic English is a selection, a simple subset of English for easy learning, intended to allow good communication early in the learning process.

World English is an attempt to label the common subset of English as spoken around the world by educated non-native speakers.

But there is no single word that captures such a subset. It seems almost impossible to have one given that what you are asking for is a qualification of English.