I’m facing the same problem. The layout of Gutenberg editor is not optimal when dealing with custom fields. Haven’t found a way to customize Gutenberg as I want.
The solution I settled for in the meantime is to change the order of the metaboxes.
Be aware though that this places the metaboxes BEFORE the title and also that your site may have more custom meta boxes than mine (Only using ACF and Yoast SEO). The metaboxes are collapsable which helps a bit…
I came across the same problem today (noticed i had repeaters with 1000s of rows) and stumbled upon this thread.
I created the following script to convert the data of a file field into a repeater. This worked when there was a file uploaded (field has data) and should be inserted into array of repeater on first position.