Problem/Motivation
It's unintuitive to configure the number of fields to display as part of the storage settings. Granted, there is a logical connection between the number of values possible and the number of fields to show, but the number of fields to show does not at any point impact the storage of the values. Proof of this is that typically the number of values stored cannot be changed once a field contains data, but it is possible to continue to change the number of fields displayed.
The configuration of this module only impacts the entity forms that use the configured field. As such, Drupal convention would hold that this configuration be provided as part of the widget settings instead of the storage configuration.
Proposed resolution
Move the configuration to the widget configuration using hook_field_widget_third_party_settings_form and then update the code to change the widget output in unlimited_field_settings_field_widget_multivalue_form_alter.
Remaining tasks
Refactor the module to use this new approach, likely removing a number of the existing hook implementations. Specifically
Add hook_field_widget_third_party_settings_form implementation for configuring the module's behaviour for a field
Update unlimited_field_settings_field_widget_multivalue_form_alter to use configured values to use widget configuration
Remove unlimited_field_settings_form_field_storage_config_edit_form_alter, _unlimited_field_settings_form_field_storage_submit, and _unlimited_field_settings_form_field_validate
Update documentation, including README
User interface changes
Site builders would need to configure the number of fields to display in "Manage form display" for a bundle, instead of "Storage settings" for the field under the "Manage fields" tab.
Data model changes
Where the configuration is stored would change. As such, this would likely justify a major version change, which could also be a good opportunity to switch to semantic versioning. Ideally, a hook_update implementation would convert existing field configuration to the new widget-based setup.