I did not support this because of the difficulty of implementation. However, Gutenberg is made with ReactJS, and a slot called PluginPostStatusInfo is provided, so it seems possible to inject your own React elements by using this slot. https://github.com/WordPress/gutenberg/blob/trunk/docs/reference-guides/slotfills/plugin-post-status-info.md
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I believe setting the coming soon as the shop page will accomplish what you want but I may be misunderstanding what you want accomplished. To set the WooCommerce shop page, navigate to WooCommerce > Settings and click the Products Tab. In the section labeled “shop page,” click the dropdown and choose your coming soon page.
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