Have you found out more Henk? I am very interested in generating my own cue sheets and I am very interested in all the available cue sheet symbols that can be used by the Elemnt units in GPX, TCX and .fit files.
To summarize your investigation,
Cues in GPX files:
<wpt>
<name></name> <<-- The symbol type
<desc></desc> <<-- The descrition that the ELEMNT will show as text in the cue sheet.
</wpt>
Cues in TCX Files:
<CoursePoint>
<PointType></PointType> <<-- The Symbol type
<Name></name> <<-- Not used by Wahoo units. Used by Garmin units with a limitation of 10-16 characters.
<Notes></Notes> <<-- The description that the ELEMNT will show as text in the cue sheet. Not used by Garmin Units.
</CoursePoint>
According to your investigation possible values for the cue symbols are:
GPX<name>: Generic, Summit, Valley, Water, Food, Danger, Left, Right, Straight, First Aid, 4th Category, 3rd Category, 2nd Category, 1st Category, Hors Category, Sprint
GPX<name>(extended, supposedly only available in .fit files but Element units can process them in GPX files): Roundabout, Slight/Sharp Left/Right, U Turn
TCX<PointType>: Generic, Summit, Valley, Water, Food, Danger, Left, Right, Straight, First Aid, 4th Category, 3rd Category, 2nd Category, 1st Category, Hors Category, Sprint
TCX<PointType>(extended, supposedly only available in .fit files but Element units can process them in GPX files): Roundabout, Slight/Sharp Left/Right, U Turn
Are there any more values?