WPML's Translation Management module makes it easy to manage the translations of the entire site, from one central admin screen.
You will be able to assign translation jobs to your own translators, or outsource translation work to translation services.
I'm trying to understand why I can't see these elements anymore.
Is there any documentation that you are following?
Not really since everything was working just fine before the last Support suggestion where I've been asked to add a line of code in the core PHP file that manage the translation.
Upon further inspection, we have discovered that the issue was being caused because some post types were set to 'not translatable' in WPML -> Settings -> Post Types Translation. I have marked them to be translatable, and after this, we could see the pencil and plus icons on the pages without problems.