When I need to do this I’ll typically make a custom property (dataset type) on the root container and call it defaultTagPens or similar.
Configure the EasyChart how you want the default config to be, go to the tagPens property and copy that dataset using the button in the dataset editor window.
Paste that dataset into your root container’s custom property named defaultTagPens.
After you do that you can set (via button or visionWindowOpened or whichever event you choose) the EasyChart’s .tagPens property to the root container’s .defaultTagPens custom property.
event.source.parent.getComponent(‘Easy Chart’).tagPens = event.source.parent.defaultTagPens
Effectively accomplishes the same thing as bfuson’s solution but the dataset is stored in a custom property as opposed to defining the dataset in the scripting (something I find to be tedious).
If it was possible I would prefer to make the custom property on the EasyChart but for some reason this option is not available in the contextual menu.