Chat has no page bar, so it had no way to switch between Personal and your teams. The Personal-or-team switcher now sits at the top of the channel list. Channels belong to the selection; direct messages, shared channels and support are listed whichever you choose.
On pages that open navigation as a floating menu, such as Chat, a long tool list squeezed the search box until only its top edge showed. It now keeps its full height and the tool list scrolls instead.