Adding a text element in between title and blocks container

Is it possible to add an additional text input before the Blocks editor? I’m trying to update my Subtitle plugin to be Gutenberg compatible, but the subtitle isn’t really a “Block” and I think it’s more similar to the page title.

Pre-WordPress 5.0, I used the edit_form_after_title hook, but in Gutenberg that’s irrelevant, so I’m wondering how to inject a new, non-block, element?

Plugin in question: KIA Subtitle

Initially Gutenberg had plans to implement subheading, See this ticket but later they deprecated it. As of now, there’s no hook to do it other than building a custom block. May be in near future you’ll find something useful.

I hope this helps