We love this plugin, very helpful for our users to have a visual of the process... The only issue we had with it is that parallel steps seem to confuse it.

I don't really have a good suggestion for how this should look, but the way it looks now just seems broken to the end user.  The first job being indented would help, maybe some kind of visual connection that suggests the jobs are in parallel...

Output looks like this

Code to trigger:

def rhj = build job: 'Main'
def tasks = [:]
tasks["T1"] = { build job: 'RHEL7_Pkg'}
tasks["T2"] = { build job: 'RHEL8_Pkg'}
parallel tasks

...