Domino Designer 10.0.1 does not contain up to date documentation, probably because translation is only done for major releases.
Up to date documentation is available here: https://www.ibm.com/support/knowledgecenter/en/SSKTMJ_10.0.1/welcome/domino_welcome.html
Please add a menu item to Domino Designer (e.g. "Online documentation") that opens the page in a browser (matching the DDE version). And on the web page, please add a link to the Java/LS API documentation. Looks like you have to use the search function to find the description of method arguments.