Cannot insert block between selected block and previous block

[markjaquith]

Describe the bug
When a block is selected, you cannot insert a block between the selected block and the previous block (you can insert one below the selected block).

Seems like a more general version of #8632.

To Reproduce

1. Add 3 Paragraphs.
2. Select the third paragraph.
3. Hover mouse between second and third paragraphs. No in-between inserter.
4. Select the second paragraph.
5. Hover mouse between first and second paragraphs. No in-between inserter.

Expected behavior
You can still in-between insert above the selected block.

Screenshots

Desktop (please complete the following information):

• OS: macOS
• Browser: Firefox
• Version 61.0.1

Additional context
Running Gutenberg @ b5490a6e2d917cf911f67bee0e7f98350a17a08e and toolbar is NOT pinned to the top.

[chrisvanpatten]

This was an intentional decision in #7168 / #7220 because the sibling inserter could get hidden below the toolbar. Admittedly it's not a perfect solution, but #7297 will add additional insertion options to the block settings menu as well.

[ZebulanStanphill]

Also note that the outcome of #6224 could result in a revised sibling inserter UI which could provide another solution to this issue.

[talldan]

@markjaquith I've got a PR open #8909 to add Insert Before and After options to the block settings menu (and keyboard shortcuts). Do you think that will resolve this issue? Let me know and I'll make sure this gets closed when that's merged.

[talldan]

#8909 now merged, so closing this.