When you create a deploy-only server adapter, point it to a deployment dir of a running WildFly server and then deploy a project (exploded war, which is the default), the server will say:

14:17:45,258 INFO  [org.jboss.as.server.deployment.scanner] (DeploymentScanner-threads - 2) WFLYDS0004: Found jboss-kitchensink.war in deployment directory. To trigger deployment create a file called jboss-kitchensink.war.dodeploy

I'm not exactly sure if the deploy-only server adapter should do this or not - how can it know if you want it or not. But Max says it should work and is a bug if it doesn't.

One workaround is to use zipped deployment in the server adapter settings. Another would be to change your server not to require the marker and deploy everything immediately. But it would be best if this just worked without any intervention.