There isn't possibility set entry-type for new entry in Credential Store.

/subsystem=elytron/credential-store=testCS/alias=aliasEntryType:add(secret-value=secretVALUE, entry-type=org.wildfly.security.credential.PasswordCredential)

{
    "outcome" => "failed",
    "failure-description" => "WFLYCTL0158: Operation handler failed: java.lang.IllegalArgumentException: WFLYELY00909: Credential store 'testCS' does not support given credential store entry type 'org.wildfly.security.credential.PasswordCredential'",
    "rolled-back" => true
}

10:30:39,074 ERROR [org.jboss.as.controller.management-operation] (management-handler-thread - 18) WFLYCTL0013: Operation ("add") failed - address: ([
    ("subsystem" => "elytron"),
    ("credential-store" => "testCS"),
    ("alias" => "aliasEntryType")
]): java.lang.IllegalArgumentException: WFLYELY00909: Credential store 'testCS' does not support given credential store entry type 'org.wildfly.security.credential.PasswordCredential'
        at org.wildfly.extension.elytron.CredentialStoreAliasDefinition$AddHandler.performRuntime(CredentialStoreAliasDefinition.java:166)
        at org.jboss.as.controller.AbstractAddStepHandler$1.execute(AbstractAddStepHandler.java:151)
        at org.jboss.as.controller.AbstractOperationContext.executeStep(AbstractOperationContext.java:940)
        at org.jboss.as.controller.AbstractOperationContext.processStages(AbstractOperationContext.java:683)
        at org.jboss.as.controller.AbstractOperationContext.executeOperation(AbstractOperationContext.java:382)
        at org.jboss.as.controller.OperationContextImpl.executeOperation(OperationContextImpl.java:1363)
        at org.jboss.as.controller.ModelControllerImpl.internalExecute(ModelControllerImpl.java:410)
        at org.jboss.as.controller.ModelControllerImpl.execute(ModelControllerImpl.java:232)
        at org.jboss.as.controller.remote.ModelControllerClientOperationHandler$ExecuteRequestHandler.doExecute(ModelControllerClientOperationHandler.java:213)
        at org.jboss.as.controller.remote.ModelControllerClientOperationHandler$ExecuteRequestHandler.access$300(ModelControllerClientOperationHandler.java:136)
        at org.jboss.as.controller.remote.ModelControllerClientOperationHandler$ExecuteRequestHandler$1$1.run(ModelControllerClientOperationHandler.java:157)
        at org.jboss.as.controller.remote.ModelControllerClientOperationHandler$ExecuteRequestHandler$1$1.run(ModelControllerClientOperationHandler.java:153)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:422)
        at org.jboss.as.controller.AccessAuditContext.doAs(AccessAuditContext.java:149)
        at org.jboss.as.controller.remote.ModelControllerClientOperationHandler$ExecuteRequestHandler$1.execute(ModelControllerClientOperationHandler.java:153)
        at org.jboss.as.protocol.mgmt.ManagementRequestContextImpl$1.doExecute(ManagementRequestContextImpl.java:70)
        at org.jboss.as.protocol.mgmt.ManagementRequestContextImpl$AsyncTaskRunner.run(ManagementRequestContextImpl.java:160)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)
        at org.jboss.threads.JBossThread.run(JBossThread.java:320)