Open the Spaces screen.
Auto-group my tabs sorts the tabs in your current window into named, colour-coded Chrome tab groups. It needs at least two ordinary web pages in the window and leaves pinned tabs alone. Ungroup all removes the groups.
To save a session, type an optional name and click Save. Every tab in the window is saved. Click the arrow next to a session to reopen it in a new window, or the bin to delete it. Sessions save each tab's address and title; they do not save tab groups, pinned state or your place on the page.