This is mostly a UX thing, but a pretty big one IMO. Currently, it's impossible to see what block type a custom block belongs to in de administration overview listing page at structure -> block layout- > custom block library.
1. Create at least one other block type (beside the default basic block) at admin/structure/block/block-content/types/add
2. Create some custom blocks at block/add using the various block types made in step 1.
3. Go to the block listing library at admin/structure/block/block-content
You will see the blocks with the block description in the first column and an operations column with the edit/delete actions. But there is no way to see what block type it is in this screen, or in any other screen.
PASSED: [[SimpleTest]]: [PHP 5.4 MySQL] 83,361 pass(es). View
FAILED: [[SimpleTest]]: [PHP 5.4 MySQL] 83,375 pass(es), 1 fail(s), and 0 exception(s). View
FAILED: [[SimpleTest]]: [PHP 5.4 MySQL] 83,359 pass(es), 4 fail(s), and 1 exception(s). View