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Essentially, I want to change:

Managing a lot of people is a very difficult problem

to:

Lot of people, difficult problem

I understand that when you shorten a title, it will become more vague, but sometimes, I feel like when you shorten it too much the meaning becomes too uncertain or difficult to guess, is there a consensus on how to do this properly or perhaps a widespread practice on how to do this properly, that I am not aware of?

It's fine to shorten but only when the reader can fill in the blank.

So far, you have:

Managing a lot of people is a very difficult problem
to
Lot of
people, difficult problem

In this example, you have 3 concepts:

1. It's about managing people


2. There are a lot of people


3. It's hard

The most important of these is the first, that your article is about management. Yet it's the one you dropped in your title revision. "Lot of people, difficult problem" can be about anything. Even if you know from context it's about a workplace (and not about, say, overpopulation), it could be about noise levels or fitting in enough desks/cubicles or the fact that you don't have enough bathrooms. All those can be legit articles about work.

I would drop the third concept, that it's hard. Because that is implied by the fact that you are dedicating an entire article to it.

This leaves you with:

Managing a lot of people

It's a boring title, but it's got all 3 concepts in it (the 3rd is implied). And it's half the length of the old one.

I'll leave it to you to make the title more interesting, and more focused (since you're presumably not covering everything about managing multiple people), because the job of Writing.SE isn't to rewrite for you. Instead, it's to help you work through it.

What are the concepts you are trying to convey? Which are the most vital? Which can be dropped because they're implied? Which can be dropped because they're unnecessary in the title?

How about... "Crowd Management Challenges"

Where "Crowd" encapsulates "lot of people"
and "Challenges" implies "is a difficult problem".

Management Difficulties Scale with Headcount

Titles follow the same rule as billboard advertisements: no more than 7 words; no matter what their size. Scientifically speaking, billboard comprehension rates drop off a cliff after 7 words.

Apply the same rule to your titles.

Your first title is a complete sentence, which is unusual. Your second title completely drops the concept of management.

Ask yourself what the core of the title is and use that. If it were me, I might distill it down to Management Difficulties or Problems in Management.

You can also add a subtitle if the main title is not enough. Management Difficulties: Effects of Larger Staff.

Your second title could apply to any gathering of people, including the audience at a rock concert. It could be about overpopulation and the problems caused by that.

Titles need not be grammatically correct. They should be clear or, in fiction, evocative.

Find some combination that properly conveys to the reader that you will discuss the difficulties caused by managing many people rather than a few.

I'd go with something short and to the point, like Challenges of managing people.

I'm not sure about putting The in front of Challenges, but I think it basically says all you want.