Google Assistant on mobile devices it gaining some new features including the ability to view past questions, as well as edit and/or delete those questions. These features do seem to be in relation to the release of Google Assistant's new keyboard functionality. At Google I/O 2017, Google announced that the Google Assistant was gaining a text input ability where users could simply type a question instead of asking one. Following which, reports starting to roll through noting that the Google Assistant was already being updated for a number of users, and with that update came the ability to make use of the keyboard. Now however, it also seems as though that update is activating the view, edit, and delete, of previous questions feature.
Up until now, the Google Assistant worked on a sort of back to default basis. So each time you launched the assistant, it launched a fresh version of the Assistant, ready to answer your new question. This is where the change has occurred as some users who are seeing the updated Google Assistant version, are also noting that previous searches are now showing up. Essentially, allowing the user to scroll back through their previous searches for easier recall. In a very similar way to how the Google Assistant works within the Allo app. In addition, it also seems as though searches (and largely any shown comment, reply, or otherwise), can now be edited, or if wanted, fully deleted. To do this, the user simply needs to long press on the comment or question to be edited or deleted, and a pop up will emerge offering the option to either "edit query" or "delete group" – the latter referring to the deletion of not just the question, but also the related answers as well.
While it does seem to be clear that the keyboard-enabled version of the Google Assistant is already rolling out, this is one of those typical Google rolling outs. So not everyone will receive the update at the same time. Likewise, there does not currently seem to be anyway to force the update, it will simply arrive when it is ready. While it is not 100-percent guaranteed that these new view, edit, delete, features are arriving in tandem with the keyboard update (could have already been available in beta to some users), the new capabilities are now being more noticed with the arrival of the keyboard update.