Hi @drunkrocketeer.
I just wrote a simple plugin based on Javascript to merge tabs from different groups. So meanwhile, until Elliot add this functionality, you can download my plugin here
https://wordpress.org/plugins/acf-merge-group-tabs/
Hi @Michael1981. Feel free to try my very simple plugin for merging tabs. It uses javascript too, but it runs before ACF initialises the content, so all tabs appear together.
https://wordpress.org/plugins/acf-merge-group-tabs/