It took me some time to find out, as the service manual does not explicit what the "drawer" is. It appears this is the lower part of the tracer, under the display and upper front panel. It's a slider assembly including Lower Key panel, Bubble memory, component fixtures holder, collector supply switch. Explanation only appears in 370B Service Manual on page 4-15. You must remove two lower lateral brackets (with adjustable potentiometers markings) held each by 8 screws (four flat-head and four round-head. And then push forward the said drawer by its rear corners.
HTH.
Christian F1GWR