ChartObjects as Outputs

Hi everyone, i would like to ask if it's possible to set certain ChartObjects, like trendlines, as outputs.

I've recently seen an indicator which was able to change color to trendlines and make them visible/invisible by changing the settings from the "Modify Indicator" form, by acting as if it was an indicatordataseries regular output. The indicator was, sadly, not open source. I would like to ask how is it possible to obtain said behauvoir.

Many thanks to everyone

          -C