3 is the maximum and it's much better than the single chroma key that had been standard for many years.
The specific answer to your situation will likely depend on exactly what your clips look like, and chroma-keying is often just one (or 3) of the steps needed to smoothly blend your media. See this PhotoDirector
post for some background and to see why sharing your actual clip(s) is crucial.
This message was edited 1 time. Last update was at Jul 06. 2020 19:07