mv-expand - I cannot make it work!!

[CodnChips]

Can anyone spare anytime to give me a basic example of how to use mv-expand please, so that I can then expand on it! (See what I did there )  I just don't get it.  I understand that it can be used to extract a value from an array, but in my fiddling it's not happening.  I have looked at the docs but the examples just don't relate\click with me.

I've been enjoying @TeachJing Youtube lessons - but I haven't found one that covers this command.

I'm just looking for the most minimal lines so I can build from it.

Many thanks (Soz for the stupid question!)

[#2]

but you bring up an interesting point, I guess I should have expanded the 'big' json and then applied strings to the individual fields....