I think the only thing you can really do is put comments in the blocks themselves indicating which block starts and ends where.
If you take a look at lib/Scoop/Interface.pm, around line 40, you'll see some commented-out code that puts an HTML comment at the beginning and end of every block. I initially put this in in the hopes that it would help admins track down what block was used where, an especially ... interesting ... task when dealing with themes.
The trouble is, some blocks, like the colours, are interpolated into the middle of an HTML tag, and putting a comment in the middle of an HTML tag breaks things horribly. The code really has no way of telling what it can and can't safely put comments around, because a block is a block and can be interpolated everywhere.
And re: the search engine for blocks - I was just thinking an hour or so ago, as I answered a "where is this block?" question on scoop-help, that having the Scoop search engine search block values and descriptions (for people with edit_blocks permission only, of course) would be nice...
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Discuss the art and craft of writing