What you can do is the following:

Click the large + button near the bottom of the content to open a new block.
Select the WPPA gallery icon. This shows you the shortcode generator.
You can configure your shortcode, but the ‘only’ problem is that the ‘insert shortcode’ button never appears, what it should do.
However, you can copy/paste the shortcode as displayed near the bottom of the dialog into a new shortcode block, and discard the block that contains the generator.

I hope you can live with this while i will attempt to fix it.
Thanx for the report anyway.

* Fixed shortcode generators. They all work back properly now, both on classic as on block editor in classic blocks as well as the wppa custom block types.