Unfortunately, you are wrong on both counts. Let's look at both of your examples.
Experimentally determined value of xxx.
Here "determined" is used as a verb. We can verify that by doing a couple of simple tests. You can grade and compare adjectives, so all we have to do is add an adverb in front of the word in question. Let me give you a very simple example:
She is a pretty girl ---> She is a very pretty girl. This is a perfectly acceptable sentence, the only difference is the degree.
But when we add "very" in front of "determined", the sentence doesn't make sense:
Experimentally very determined value of xxx - this doesn't make sense. Besides, value doesn't have feeling, so how can it be determined (as in adjective resolute. unwavering). Strike one against adjective.
Another test we can do is by re-arranging the sentence:
The value was determined experimentally, or the value was determined by experiment. It is obvious then, here "determined" is a verb. Strike two against adjective.
There are other tests you can do but with two strikes already we don't need to go any further.
The highlighted part of the context (sic)...
Again, "highlighted" is used as a verb. Let's do the same tests:
The very highlighted part of the text... - This doesn't make sense. A text is either highlighted or not highlighted, you can't say that it is "very highlighted". Strike one against adjective.
In fact, you can try another adverb:
the mechanically/chemically/electronically highlighted text - this makes it clear that "highlighted" is a verb here.
Going back to your original sentence in question:
A determined group of people - a very determined group of people. Makes perfect sense, the only difference being the degree.
There are exceptions, but they are not similar to what we are discussing so I am not going to get into them.
We can go on and on, but when in doubt you can always check the dictionaries. Dictionaries such as Oxford and Cambridge usually list the words separately for noun, verb, adjective, etc.
If you look up "determined", you will see it in verb and adjective with sentence examples. And the dictionaries are very clear on the meaning of determined as an adjective - resolute/unwavering, which was clearly not the meaning you intended in your original sentence.
If you look up the word "highlighted", there is no mention of it being an adjective at all.
So, to recap:
1. "determined" as in "a group of determined people" is an adjective, and it means the group of people are resolute in whatever they action they are planning.
2. "determined" as in "experimentally determined value of xxx" is a verb, and it means the value of xxx was determined/decided by experiment.
3. "highlighted" as in "the highlighted part of the text" is a verb, and it means the text was highlighted by some means.
By the way, the paragraph in red is not structurally similar to the other one. Their structures start to diverge after the first coma.