Maximum Limit of nodes in Process Model

AFAIK there is no hard limit, but best practices and design guides.

May I ask what your concern is?

As with all of the Best Practices and Guides they are not hard limits, but guidance. You always have to consider the context in which you're considering these values, and have an understanding of why such limits are even being suggested. You can then make risk-based decisions as to whether you need to address the recommendations or not. Because, in the end, it's about risk management: the likelihood, and the impact, and what (if any) mitigations you choose to apply. 

Just repeating the same core message in other words:
Not just something is technically possible means automatically you should do it.
Best practices are giving guidances how to solve certain situations the most suitable way.

The PM that goes over 50 nodes could be practically unusable.  Many of us have made PMs that have 2.  Start and End.  An ideal average would probably be somewhere between 5 and 10.

Ask yourself why the switch from recommending less than 50 to recommending less than 38 would be of concern, and if that doesn't point to something more concerning.  Just because you can doesn't mean you ever should.

Best practice is to create short lived process models (not more than 30 nodes). 

Hi [mention:eb9a70f0b32a430e8819bff3623248f0:e9ed411860ed4f2ba0265705b8793d05] , On a short note - There is no strict limit for this, but according to best practices, the recommended number is 50. We can add as many nodes as needed, but doing so may raise warnings or performance issues due to the large process, and we would have to manage those consequences. That's why, as per best practices, the ideal number is 50, and we are splitting the tasks into subprocesses.

Appian suggest not to use more than 30 nodes