I am looking for some training videos on JBPM Suite v6, in order to prepare for the certification program.
Can anybody provide me a lead on that?
What you want is JB427.
If you want online training, it's available in RHLS, or as an a-la-carte course, in two modalities - as a self-paced course, or as a video classroom (VC).
(Side note - if you take the VC, you'll be seeing my face quite a bit. :))
The price will depend on your country, so it's best if you have a look at the JB427 web page and select your country from the drop down menu on the right.
It is noteworthy to point out that BPMS has been renamed in its new version to Process Automation Manager (PAM), which is now in version 7.1. I'm saying that because Red Hat JBoss BPM Suite 6.x will be ending Maintenance Support in Dec 2019 (see here). I wouldn't necessarily recommend to start with BPMS 6.x at this point. I have seen some 7.x courses, though I don't think RH has created the exams and certifications just yet.
Indeed, JB427 is the course based on the 6.x generation of the product.
The essentials didn't really change that much from 6 to 7 though - have a look at the BPMS to RHPAM Migration Guide, specifically at chapter 5 which is on migrating Java projects. Everything else in that guide is about migrating existing Business Central projects to a new installation of PAM.
The way you model processes in BPMN2 did not change a bit (as BPMN2 is a standard), what we did get is some new choices in the modeling arena with support for DMN and PMML models (but no open-source tooling yet).
You are also correct in pointing out there are two new courses, but those join both DM (Decision Manager) and PAM (Process Automation Manager) into one course.
There is currently no directly related certification and I do not know of any plans to have one - however, EX427 and EX465 are still the authoritative exams on BPM and business rule authoring, respectively.
Whether the existing exams will be updated to 7.x or new exams are released is absolutely not my guess to make, but I assure you something will happen soon.