There are several options:
--show-members:value
--show-types:value
 --show-packages:value
--show-module-contents:valu
--expand-requires:value

They are use colon to separate option from argument

Some other javac related options don't support "=" as separator
javadoc --module-path=.
javadoc: error - invalid flag: --module-path=.

javadoc --module-source-path=.
javadoc: error - invalid flag: --module-source-path=.