While I think we do a disservice to the Proverbs by only reading them as individual short statements and not considering the whole book, this is highlighted as a problem in Proverbs 30. Too many of these verses are the completion of thoughts in the prior verses. It is necessary to read it in large groups to comprehend the point.
After all, we must not forget that the Bible was written word-by-word and line-by-line, but not verse-by-verse and chapter-by-chapter. Those divisions are later editorial aids for later readers. Read Scripture in thought units, like paragraphs, to better grasp the point.
In Proverbs 30 we see this illustrated in groups like these: Proverbs 30:1-4; Proverbs 30:11-14; Proverbs 30:21-23. With these examples, you should be able to notice the other groups of verses that represent full thought units in the chapter.
Let us take a look at Proverbs 30:21-23 for today. The first is a typical idiom that occurs elsewhere in Scripture (Amos, other places in Proverbs come to mind), where you start with a number and then increase it by one to set up a list. Here it’s a “under 3 things, even under 4,” though the same phrasing works with any other numbering. It’s a rhetorical device for emphasis. There is no cause to go hunting for the other 3 or to assume there should be 7 total here.
I am searching for any source which indicates that the fourth item should be regarded as more significant, and the UBS Handbook series in my Logos Bible Software acknowledges the possibility. If it is relevant, then we would see emphasis thrown onto the maidservant that supplants her mistress, which is a decent warning to a future king. Especially if Solomon is highlighting problems for his successors to avoid.
This would require seeing the Hebrew as showing a building of emphasis rather than the more typical parallel, but that is possible. Some translations see it as simply rhetorical.
Considering these four things, though, let’s look at them. They all involve the reversal of roles or the accession to power without process. That’s the big issue at stake: individuals who attain great power without passing through responsibility to get there.
Expand that as you look around you. While I am no fan of lifelong politicians, there is something to be said for people with a history of service arising to leadership over hacks who can draw voters with charismatic cluelessness. Likewise, we can see it in churches when we let people who have never served become leaders.
There is a need to test first, then allow people into power. Otherwise, trouble comes. Especially if power is attained through deception, like the last case in Proverbs 30:23, where lies were part of the equation.