truncatechars from start + slice from end

Using Django Getting Started
1

Is there a better way to do this ?

<a href="{{ url }}">
    {{ url|truncatechars:20 }}...{{ url|slice:"-20:" }}
</a>
2

Do it in the view and pass it as a separate value in the context?

Create a custom filter?

3

I tried to create a custom filter but always returned

return parser.libraries[name]
KeyError: 'custom_filters'

My templates are not in the app and I have 5 apps where I want the custom_filters to be accessed from any of the apps.

4

Custom tags and filters are not specific to any app. They are available anywhere in the project.

See How to create custom template tags and filters | Django documentation | Django