Circling back to this, for any other noobs who might end up here…
@texnixe got me on the right track. I found that the default fieldset available to Layout, when none is specified, simply doesn’t include the table field—probably because a table needs those other files set up. To override the default fieldset you have to specify all fields you want available. Including ‘table’ in this fieldset (in about.yml, in my case) makes the table option appear when adding a block in Layout. It uses the kirby/site/blueprints/blocks/table.yml and
kirby/site/snippets/blocks/table.php that I had set up, per table | Kirby CMS.
Excerpt from about.yml:
layout:
label: Layout
type: layout
layouts:
- "1/1"
- "1/2, 1/2"
- "1/3, 2/3"
- "1/3, 1/3, 1/3"
fieldsets:
- heading
- text
- list
- table
- image
- gallery
- video
- code
- markdown