Hopefully what I am going to write is version agnostic. BTW, I am using Ami 5.0.0.
1. Need to create a new file for this custom indicator or whatever you call it. Ami calls it a formula. This you can do by clicking on charts tab on the left-top pane (which has other tabs like Symbols, Layouts, Charts etc). Select the folder under which you want this to be in. Right click, go to New and then to Formula.
2. The editor should open up. And punch in the following:
Code:
Plot(Trix(9), "Trix(9)", colorRed);
Plot(Trix(15), "Trix(15)", colorBlue);
Save the file. And then click on the apply indicator, to get it in a pane by itself.
3. In order to Overlay the same, right click on the file you just created and select overlay. In fact you should be able to drag and drop the same as well.