All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
A man saying to his ex-wife: “I want to work on things” is not considered as taking her back because it is not an explicit formula of taking her back and it is not one of its metaphors. Hence, if the husband wants to take his wife back during the waiting period, he may take her back by saying: I am taking you back or I return you, and it is desirable for him to have witnesses to the taking back.
The preponderant opinion in our view in Islamweb is that taking back the wife occurs once intercourse happens with the wife during the waiting period.
Allah knows best.