Nested Marker icons are sorted alphabetically among any regular icons.
Per default, the first icon within that sub-folder represents icon for the nested Markers.
There are two ways to specify such a custom icon:
 | Rename an icon in your sub-folder to sort it in front - which affects the tag entered by that icon. |
| Add an icon to represent your sub-tags to the top-level folder (the one holding the sub-folder) AND name it precisely like the folder holding your sub-tags. |
Like explained in Nested Markers.
The moment you click an icon that is a reference to a set of sub-level icons, the content of your Marker section changes accordingly - displaying the Markers from the sub-level folder.
Example
Within the demo Coding System folder 'Medical', there is a subfolder named Medication located. Additionally, an icon with the same name is present as well:
During a session, the Medication icon is visible among the other Marker in the 'Marker' section:
The moment you click Medication, the icons contained by the subfolder appear:
Now you can pick the applicable medicine, for entering into the log file.
The additional arrow icon enables you to return to the previous marker-level: 
If your Coding System has more than 2 levels, you can immediately return to the top-level-markers with an automatically created additional Home icon:
