It happens a lot that people on a project, including me, forget to change the labels or the buttons for the different languages that are configured.
Would be nice if the labels and the other elements that need translation, will be colored red or some other kind of awareness.
Your idea is already in place in the Modeler: in the warnings. Keeping your warnings to a minimum, you will automatically come across missing translations.
Why don't you enable the 'check completeness' flag for those languages?
Great idea. Note that this would not work for Dutch because the modeler fills in default translations for buttons, labels and a few other components as well. For the translation tool, it would appear that the translation exists, where it really is a default like ' Action' or an altered version of the called microflow.
I registered that here: https://forum.mendix.com/link/ideas/1018
I know that this is the case and that here are ways to see where the translation is missing, but the whole idea of this post is that people forget to switch languages and therefore they forget to fill in the translation. When it throws some kind of awareness people will not forget to fill in the translation.
If you switch your language in the modeler to the language you want to check, texts that aren't translated are surrounded in <>.