I don't understand this. You need to use Java 8 or the doclet can fail. SLC uses the compiler path set in the B4A IDE. Temporarily change that to Java 8 to use SLC.
BTW, there is a version of the doclet tool that works with Java 11+. It was required for jServer, however it doesn't support all features so unless it isn't possible, you should use Java 8 with SLC.