Heh, sorry, but the non-translators are missing the translators' point.
We don't want to delete text and substitute our own. We want to see the text we are substituting ours for, as we do it.
If we have deleted the text we are translating, we can no longer see it. We can't actually memorize a document sentence by sentence - look at a sentence, memorize it, delete it, then type the equivalent in the new language.
We do use a mix of overtype and insert, since yes, lengths vary, and also word/phrase order differs -- so, for instance, I may start out a sentence in insert mode (because a phrase that is mid-sentence in the French needs to be at the beginning of the sentence
in the English, but I don't want to type over the part of the sentence it will then precede), and then switch to overtype for the rest of the sentence and delete the straggling bits at the end of the original sentence, then start over on the next one. Because
the order often varies, we do not work one word or phrase at a time, which would be insanely time-consuming anyway: delete a word/phrase, type the corresponding word/phrase, delete the next word/phrase, type the corresponding word/phrase ... aieee.
Trust us when we say what *we* need. ;) No, we would not find that process less error-prone. I've been translating for nigh on 40 years, and I know what works and what doesn't!
The thing here is that, like many things in this world, PowerPoint has been designed for USAmerican users. Translation is not a big factor for them. Out here in the rest of the universe, many users work in more than one language - multinational corporations,
international organizations, public and private sector entities in bilingual/multilingual countries, etc. For instance, I am about to start working on an 80-slide PPT presentation by a Canadian law firm for a bilingual (FR/EN) conference on recent developments
in corporate law. A US law firm would seldom have similar materials translated; in Canada, this kind of material, whether from government, bar associations, law firms or academics, will commonly be translated from French to English or vice versa. Translation
really is a big factor for many users.
By the way (re the original answer here), as far as I know (although I am not using the latest Word), overtype is still readily accessible in Word. The day it is done away with is the day I retire!
Those of us who have investigated this flaw in PPT have resigned ourselves to it, but I'm sure that new translators will continue to come along and wonder why this useful - virtually essential - function has been omitted from it. Q&As like this at least
answer the question of how to find the function: it isn't there.