Note: this list is generated by looking for the string for this theme hook, so it may include some references that are not actually using this theme hook.

field_ui_field_edit_form in core/modules/field_ui/
Form constructor for the field instance settings form.
file_settings_form in core/modules/file/
Form callback for file settings.
link_field_instance_settings_form in core/modules/link/link.module
Implements hook_field_instance_settings_form().
node_type_form in core/modules/node/
Form constructor for the node type editing form.
path_patterns_form in core/modules/path/
Form builder; Configure the URL alias patterns.
path_pattern_settings_form in core/modules/path/path.module
Return the URL alias pattern settings form for easy addition into other forms.
system_site_maintenance_mode in core/modules/system/
Form builder; Configure the site's maintenance status.
system_theme in core/modules/system/system.module
Implements hook_theme().
user_settings_email in core/modules/user/
Form builder; Configure user email settings for this site.