"J'ai mis mon parapluie dans ton sac à dos."
Translation:I have put my umbrella in your backpack.
Perhaps I am mistaken, but I feel that the non-composite "put" can also be the English preterit (in addition to being the simple). That is, "I put my umbrella in your backpack" should be a valid translation. It is definitely normal English for a past action, whereas it would be awkward for a present action (which would be "I am putting my umbrella....".
If I'm wrong then I'd like to understand the distinction between "have put" and "put" for a past action in English.
Yes, "put" may be either present tense or preterit. For clarification, the default sentence was entered as "have put", but "put" is equally acceptable. No excuse but we had almost no notice that Duo was planning to initiate a test of the new course and there was a mad dash to flesh out a lot of the new material. In the process, many sentences were put in rather hurriedly and did not include all the normal variations. This exercise has been checked and should address your concerns. I.e., even though it may display "have put", the option without "have" is also accepted.
Have put and put are both versions of the perfect tense in english however I think it is because put is also present. The have actually creates the distinction between present and past. Saying that, I also got it wrong and I put should still be accepted because it makes sense.