This is the text
[Interim Review[s]] are g[iv]en [by m[a]in head] and [no one e[lse has] th]e access
The regex must be in the format
[Interim Review[s]] are g[iv]en [by m[a]in head] and [no one e[lse has] th]e access
You can see that the inner brace which is having outer brace must be highlighted. The one which has only a single brace without outer brace must not be highlighted. You can see in the format given in the question that in g[iv]en [iv] must not be highlighted as it does not have an outer brace. But in [Interim Review[s]], [s] must be highlighted and in [by m[a]in head], [a] must be highlighted and in [no one e[lse has], [lse has] must be highlighted.
I have tried the regex [[^[]]*], you can see in https://regex101.com/r/xR0wM3/5, but it is selecting the brace which does not have outer brace also. Which is not the required output
you can try this out \[[^\[]+?]
You may want to use a capturing group:
\[[^\[\]]*(\[[^\[\]]*\])[^\[\]]*\]