I am new to Eclipse which I use primarily for Java. I have previously used IntelliJ Idea in which it is possible to select a variable which extends Iteratable (Collection, List
As far as I know Eclipse does not support that in the way you describe.
If Eclipse does not find the right variable you can use the tabulator key to iterate through the placeholders in the foreach template. At the iterable point eclipse will show you a list of iterables you can choose from.