I've noticed that several guests (and friends who are guests with other hosts) have been having issues with the new Trips UI.
Primarily, mid-trip, the UI goes to a screen for each trip that does not list the reservation, nor have any obvious roadsigns to the reservation info.
Clicking on the first date of the trip will add a box with reservation info. Clicking on the final date should also do so, but for me appears to bring up the next reservation if there are multiple reservations with the same host.
Finally, for those trying to get to a way to alter a reservation, https://www.airbnb.com/alterations/ postpended with the reservation confirmation code will lead to the cancel/alter page, AFAICT.
Hope this helps some of you,