The Problem was because of a bug in elytron.bat in Wildfly 26.0.0 (JBEAP-23015)
By using Wildlfy 25.0.1.Final Version it was possible to create a credentialstore and add a password credential in a batch file.
elytron-tool.bat credential-store --create --
location="%appserver_home%/standalone/data/mycredstore.cs" --password StorePass
elytron-tool.bat credential-store --
location="%appserver_home%/standalone/data/mycredstore.cs" --password StorePass
--add=database-pw --secret=myDBPassword
To refer this credential store in standalone.xml
<credential-stores>
<credential-store name="mycredstore" relative-to="jboss.server.data.dir"
path="mycredstore.cs" create="true">
<credential-reference clear-text="StorePass"/>
</credential-store>
</credential-stores>