It is suggested (by
@Erel ), that the SDK Manager does not
need to be used.
For B4A to function, all necessary items at known working versions are included in the downloads accompanying the B4A setup.
Using the SDK Manager indiscriminately
might cause difficult to identify compatibility issues and/or outright failures.
That said, I have often installed the Recommended Items without
noticeable issues, but my use of B4A is (still) very modest and limited.
The safest answer overall though is: "Don't use SDK Manager unless you understand WHY you need to use it."