When using the Custom Search Blocks feature of Custom Search, in the Custom Search configuration > Search Blocks tab, set the number of blocks to 3. Configure those three blocks as you please. Then go back and decrease the number of blocks to 2. The block is removed from the list of blocks at admin/structure/block, but can still be accessed directly, and will still show up on pages that it's been configured to appear on.
By default, Custom Search blocks cannot be deleted, so even if we increase the number of blocks back to 3 and re-instate the previously existing block, we cannot delete it or remove it.
Either the last custom search block should be deleted when decreasing the count, or there should be a more finely-tuned ability to manage additional custom search blocks.
Closed: outdated
1.16
Blocks submodule