What is the relationship between the sub-items and the main one on Oxford Dictionary?

Question

Oxford Dictionary (https://www.lexico.com/en/definition/just) gives a bunch of definitions about “just”

there are 3 sub-items in 4th item, one of them is pointed out by blue rectangle in the following image.

What is the relationship between the sub-items and the main one?

Could all of 3 sub-items could be a piece of meanings of "Simply", I guess not.

sub-item 4.2 gives

Used as a polite formula for giving permission or making a request.

and gives this example

just help yourselves

if this is one piece of meanings of the main item, namely, "Simply", the following sentence would sound normal

Simply help yourselves

which actually sounds uncommon, any ideas?

Besides, neither Oxford dictionary (https://www.lexico.com/en/definition/simply) nor Cambridge dictionary (https://dictionary.cambridge.org/dictionary/english-chinese-simplified/simply) has a piece of meaning similar to this one (shows politeness).

Answer 1

All three sub-usages are clear substitutes for simply - each one in a slightly different way.

4.1: they're just great

Their condition of being great is not bound to a complicated formula like they're kind of great but with the exception of ... and actually.... No, they are great. Period. It's this simple. They are simply great.

4.2: just help yourselves

Don't go the complicated way of asking someone for help. Take the simple way. Simply help yourselves.

4.3: it might just help

I don't know. You perhaps need a complex solution. But it could also be that this simple solution works for you. This could simply be your solution. This might simply be the help you need. This might simply help.

Of cause, we don't think of 'simply' or 'just' in such a detailedness when we use them. We use them intuitively, but the intuition checks the appropriateness of the usage against such thoughts in a quick, unknown, but reliable manner.