We can have autocomplete feature for user input's area, where it provides suggestions to user from the FAQ list for a particular chatbot. It can also have autocorrect feature, where it corrects spellings of user's input.
Thank you very much for raising this feedback. There is a concept of custom controls which allows you to build your own control. OOTB there is support for such controls which are generic in nature e.g. date picker. Autocomplete which has to be connected to your data source requires to be aware of a context and use case where it is going to be used. This is the reason why it is not available as OOTB control.