Will this fix address this problem: JENKINS-28382 ?
The fact that I cannot easily delete a workspace has been the biggest blocker for me using the workspace plugin.

This will allow you to clean a workspace from within the workflow script. Out will not help with showing any actions.

Right, JENKINS-26138 is a distinct issue, though one common use case for wanting to manually Wipe Workspace on occasion (to fix “sticky” build failures) is better handled by either using the new step, or (preferably) selecting the option in your SCM plugin to clean unversioned files (e.g., git clean -fdx equivalent).

Code changed in jenkins
User: James Nord
Path:
CHANGES.md
aggregator/src/test/java/org/jenkinsci/plugins/workflow/steps/DeleteDirStepTest.java
basic-steps/src/main/java/org/jenkinsci/plugins/workflow/steps/DeleteDirStep.java
basic-steps/src/main/resources/org/jenkinsci/plugins/workflow/steps/DeleteDirStep/config.jelly
http://jenkins-ci.org/commit/workflow-plugin/18812f0360697345fd2065ea769a86dcdd10b08c
Log:
[FIXED JENKINS-30346] Added a deleteDirStep to wipe out a directory

Code changed in jenkins
User: James Nord
Path:
CHANGES.md
aggregator/src/test/java/org/jenkinsci/plugins/workflow/steps/DeleteDirStepTest.java
basic-steps/src/main/java/org/jenkinsci/plugins/workflow/steps/DeleteDirStep.java
basic-steps/src/main/resources/org/jenkinsci/plugins/workflow/steps/DeleteDirStep/config.jelly
basic-steps/src/main/resources/org/jenkinsci/plugins/workflow/steps/DeleteDirStep/help.html
http://jenkins-ci.org/commit/workflow-plugin/aa620904ac26985b5a28cd3c836d734a36f382ca
Log:
Merge pull request #204 from jtnord/JENKINS-30346

[FIXED JENKINS-30346] Added a deleteDirStep to wipe out a directory

Compare: https://github.com/jenkinsci/workflow-plugin/compare/0d3a4fd8aa9b...aa620904ac26

This does not address JENKINS-26138, but it is a closer step to solving it.

Can I use a parameterized build, along with your change to the workflow plugin to do the following:

(1) I have a workflow.
(2) With the workflow, I have a build parameter, "do_clean" which by default is set to 0.
(3) If "do_clean" is set to 1, then logic in the workflow will be triggered which cleans out the files,
otherwise if "do_clean" is set to 0, then no cleaning occurs.

If this is possible, could you post a code snippet of a workflow which does this?

Thanks.

Sure you could use a boolean parameter for that purpose. Best to ask in user forums (user list, StackOverflow) for help though.

OK, I asked here: https://groups.google.com/forum/#!topic/jenkinsci-users/XqCz4pyp6_g

Code changed in jenkins
User: James Nord
Path:
aggregator/src/test/java/org/jenkinsci/plugins/workflow/steps/DeleteDirStepTest.java
basic-steps/src/main/java/org/jenkinsci/plugins/workflow/steps/DeleteDirStep.java
basic-steps/src/main/resources/org/jenkinsci/plugins/workflow/steps/DeleteDirStep/config.jelly
http://jenkins-ci.org/commit/workflow-basic-steps-plugin/bf493b14ac8e814fe5bbad9bd6af205eeba953ae
Log:
[FIXED JENKINS-30346] Added a deleteDirStep to wipe out a directory

Originally-Committed-As: 18812f0360697345fd2065ea769a86dcdd10b08c