yes, it is possible to use external libraries, seems like you want to use lodash in a script
NOTE: helpers and scripts are different, helpers are just functions that you can use in the template engine that you are using (handlebars, jsrender, jade, etc), think of it like normal handlebars helpers, scripts are functions that you can use for very different things outside of template rendering (that's why they have beforeRender and afterRender)
here you have a configuration example:
{
....
"tasks": {
...
"allowedModules": ["lodash"]
...
},
"scripts": {
....
"allowedModules": ["lodash"]
...
}
...
}
in the config you can see two different properties, tasks.allowedModules allows modules in helpers functions, and scripts.allowedModules allows modules in scripts functions, so i guess that you are not setting the value in scripts.allowedModules.
seems like the documentation is not very clear about this (tasks.allowedModules is not even mentioned in the docs), i will add more notes to it.