Old question but still a thing.
I'm unsure whether your question relates to fields within the Locomotive CMS Back Office or on the front end so I've addressed both below.
Front End
Irrespective of whether or not you're dealing with Locomotive CMS content types, either of the following will allow selection of multiple values on the front end:
- Listbox (
select element with the multiple attribute)
- A series of checkbox inputs with the same value in the
name property
Back Office
If you need to allow selection of multiple values within the Back Office, you can do this for content types using the has_many or many_to_many content type relationships.
If you need multiple value selection outside of content types (e.g. in metafields schema) you're unfortunately out of luck.