Markers can be added to continuous axes. Most often those markers highlight a deadline, a break-even-point or something similar.
They can be applied to Number or Date axes.
A marker can be of type 'Line' or 'Area'. A line-marker draws a single line at the configured position of the axis whereas an area-marker colors an area between two configured positions of the axis.

Showing the type of marker.

Sets the start value/date for the marker.

Sets the end value/date for the marker. Only necessary for area marker.

Sets the color/width/style of the line or the area.

Adds an area or line marker to the list.

For percentage axis you must provide a value between 0 and 1.

Markers can use formulas to dynamically determine its value at runtime.
When a formula and a value is specified, the formula is evaluated at runtime. When it successfully returns a value, that value is taken. Otherwise the given value is used (which is zero when no value was set).

Note:

• The chart-preview does only consider the specified value, the results of formulas will not be visible.
• The database-fields in the formula(s) does not reference the data of the report, but the data of the chart. This can be a problem when placing the chart in the Report Header or Report Footer and trying to mark something with an aggregated (grouped) value.
  For example when trying to mark the average of all values displayed in the chart, " average({#aggregatedDataField},{table.groupValue})" will not work.
  Referenced database-fields will always return the first value of the chart's group when placed in the Group- or Report-Header and the last value of the chart's group when placed in the Group- or Report-Footer.
  To get the average from all displayed values, create a new Summary Field in your report which sums up or aggregates the data grouped by the category used in the chart and use this Summary Field in the marker-formula: "average( {#aggregatedGroupedDataField}) ". This makes it possible to nest the aggregated value, for example to get the "average" of the "sum" of offers "per company".