Short Description

In product setting:

Result:

Choosing the metafield (version 1.3.0)

The Description block reads this content through its Short description metafield setting. The default key is custom.short_description.

Keep the default key above and it works with no extra setup.
Or rename it: create the metafield under your own namespace.key (for example, your brand name), then set Short description metafield to match.
Reuse on one page: create one metafield per copy (for example custom.short_description and custom.short_description_2) and point each Short description metafield at its own key to show different content.