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No new hooks added in 5.5.1 Below are recently added.

jetpack_subscriptions_comment_form_submission

hook (action): Fires on each comment subscription form submission.

Related to Modules:
Source: modules/subscriptions.php:691

jetpack_force_enable_gallery_widget

hook (filter): Allow the Gallery Widget to be enabled even when Core supports the Media Gallery Widget View Example

Related to Modules:
Source: modules/widgets/gallery.php:439

jetpack_google_translate_widget_layout

hook (filter): Filter the layout of the Google Translate Widget.<p>3 different integers are accepted.</p> <pre><code>0 for the vertical layout. 1 for the horizontal layout. 2 for the dropdown only.</code></pre>

Related to Modules:
Source: modules/widgets/google-translate.php:85

jetpack_disabled_raw_options

hook (filter): Allows to disable particular raw options.

Source: class.jetpack-options.php:439

jetpack_sync_capabilities_whitelist

hook (filter): Filter the list of capabilities that we care about

Related to Modules:
Source: sync/class.jetpack-sync-defaults.php:439

site_settings_update_wga

hook (filter): Allow newer versions of this endpoint to filter in additional fields for Google Analytics

Source: json-endpoints/class.wpcom-json-api-site-settings-endpoint.php:515

jetpack_wga_classic_custom_vars

hook (filter): Allow for additional elements to be added to the classic Google Analytics queue (_gaq) array

Source: modules/google-analytics/wp-google-analytics.php:144

jetpack_masterbar

hook (action): Fires when menu items are added to the masterbar "My Sites" menu.

Source: modules/masterbar/masterbar.php:993

jetpack_removed_user_from_blog

hook (action): Fires when a user is removed from a blog on a multisite installation

Source: sync/class.jetpack-sync-module-users.php:368

jetpack_user_edited

hook (action): Fires when a user is edited on a site

Source: sync/class.jetpack-sync-module-users.php:163