The Vary Width Markers... menu item appears in Illustrator’s main Object > Path
submenu:
Very Width Markers Menu Item
The menu item will only be available (ungrayed) if the selection contains one or more paths; however these do not need to already be of variable width. Choosing the menu command brings up the Vary Width Markers dialog:
Very Width Markers Dialog
The varied markers are created randomly; each time a parameter is changed, a different random seed will be used to create the marker variations.
Specifies the minimum width, as a percentage of the original width, that a new width marker can randomly be assigned. It can range from 0% (new markers can be all the way down to zero width) to 100% (new markers will never get smaller).
Specifies the maximum width, as a percentage of the original width, that a new width marker can randomly be assigned. It can range from 100% (new markers will never get bigger) to 1000%.
Very Width Markers Min. and Max. Examples
Specifies the space between the new varied width markers along the path, from 1 pt to 144 pt. Caution should be used when applying small values to long paths, as Illustrator may have trouble with paths that contain very high numbers of markers.
Very Width Markers Spacing Examples
Specifies the mode used to handle existing width markers when using Vary Width Markers on a stroke that is already variable width:
In Replace mode, the original stroke width profile is used to set the initial widths of the new markers, which are then randomly varied. The original markers are not kept.
In Merge mode, the new markers are initially set to the average width of the existing stroke (i.e., as if it were uniform width), and then randomly varied. This mode is generally only useful when adding a variation with large spacing over an existing variation with fairly small spacing.
In Leave Unchanged mode, new markers are added (unless they are too close to an existing width marker) with their initial width set to the current stroke profile’s width at each spot; only the new markers are then randomly varied.
Very Width Markers Existing Marker Handling
When enabled, the width added or subtracted randomly from the new width markers may be unequally distributed on the left and right, creating non-centered markers:
Very Width Markers Vary from Side to Side
When enabled, the selected paths are updated on the screen to show how they would appear if they received varied markers using the current settings. The control can be toggled on and off to force a new random seed to change the variation without changing any parameters.