The course editor shows real-world U.S. Coast Guard aids to navigation (ATONs) -- buoys, lights, and daybeacons -- on the chart alongside your own marks, using the Coast Guard's own published Light List data. This is separate from, and layered on top of, the marks you create yourself.
Identifying an ATON as your mark
Click any ATON on the chart to open its info popup, which shows its name, Light List number, and characteristics. If it's one you actually round or use in your courses, click Identify this ATON as our mark in that popup. This opens the mark editor pre-filled with a suggested code and description, and a color/shape guess based on the aid's real daymark and color banding -- you can adjust either before saving. The mark's position is locked to the ATON's own charted location rather than being freely draggable, since that position comes from the Coast Guard data, not from you.
If another org has already identified this same ATON as one of their marks, you're offered an alias instead of a brand-new mark (see below), so the same physical aid doesn't end up as two disconnected mark rows.
Aliasing an existing mark
Aliasing lets your organization keep your own code and description for a mark while its actual position always follows another mark (typically one already linked to an ATON) -- useful when your org and another both round the same physical buoy but call it something different. From the mark editor, use Convert to alias of an ATON to pick a nearby aid and link to it. Once aliased, a mark's position updates automatically if the underlying mark or ATON moves; you never need to re-enter it.
A mark that's an alias, or linked to an ATON, shows a small badge next to its code wherever marks are listed -- a chain icon (⛓) for an alias, or an anchor icon (⚓) for a direct ATON link. Hover over either for details, or click it to see the mark or aid it points to.
Duplicate marks
If the same physical mark was accidentally entered more than once (by your org or another), an organization administrator can merge the duplicates from the admin marks page, so course legs, exports, and everything else automatically point at the single surviving mark.