This project seeks to provide a true compound field solution for Drupal 7. As much as I love Field collection, it still has to save actual entities, and can cause performance problems due to having to load all the referenced field collection entities on node, or parent entity load.

View the demo preview on YouTube

Limitations

The sub-fields inside the multifield are limited to one value. You can have a multiple value multifield, but the individual fields in in the multifield can only have one value.
You cannot have a multifield inside another multifield.
I've tried to test this with all the core field types, but more advanced fields may cause issues. I haven't run into any yet, but just be aware and test what you want to use.
I will be the first to admit, this solution is doing all kinds of unholy things to Drupal's field and entity APIs, so there may be unexpected dragons laying around that I haven't discovered.

Known issues

Does not yet support the sub-fields in Views API and Entity API
- #2041533: Add Views API integration for the multifield field type
- #2041531: Add entity property API integration for multifields
#2217045: Private files always result in access denied

Recommended Modules

Multiple Value Widget: Improves the UI for managing complex multiple-value field widgets by using jQuery UI tabs.

Comparison to similar modules

Composed Field: Stores field values as serialized data. Hard to expose sub-fields in Views, Search API, etc.
Field Collection or ECK + Inline Entity Form: Stores field values as a reference to a sub-entity which contains the actual sub-field values. Adds additional layers of entities and fields.

Related links

RTBC issues for Multifield

Filters