Screenshot from the linked page, showing the Xargon level editor running on Windows. There's a pane of individual object tiles down the left side of the screen, while the right two-thirds show a zoomed-out view of the level, with certain objects highlighted.
https://digipres.club/system/media_attachments/files/113/071/004/851/535/769/original/a537057373d4dcce.jpg