jinsp is a Linux terminal-based interface (TUI) for browsing and inspecting JSON data. It allows navigation through a JSON file's tree structure using Miller columns (in a manner similar, for instance, to that of the ranger file manager).
The rightmost pane shows a flattened (read-only) preview of the currently selected element rooted at the position shown on the top line (initially the root element).
Any combination of these operations can also be performed using the mouse, by clicking on any given element (within all panes except the rightmost). Note that clicking on the currently selected element will alternate between previewing and expanding it (navigating to one of its children).