User blog comment:Googleaarex/Make an extension of the notation/@comment-5029411-20140926211035/@comment-25371339-20140928235539

Extension:

a[-]-b = a{{...{{{-}-}-}...-}-}-a with b levels

a[--]-b is next separator.

Then:

a[[-]-]-b = a[{{...{{{-}-}-}...-}-}-]-a with b levels

etc.

Limit is a[[...[[[-]-]-]...-]-]-b