The following roles grant access to source control repository operations such as importing applications from source control, or linking an application to source control:
source_control. This is a role that allows users to perform basic source control operations, such as importing an application from a source control repository, updating an application from a source control repository, or committing changes to a source control repository.
admin. This is a role that grants full access to all the features and functions of the ServiceNow platform, including source control operations. Users with this role can also perform advanced source control operations, such as creating or deleting source control repositories, configuring source control properties, or resolving conflicts.
The following roles do not grant access to source control repository operations:
source_control_admin. This is not a valid role in ServiceNow. There is no separate role for source control administration, as this function is included in the admin role.
git_admin. This is not a valid role in ServiceNow. Git is a specific type of source control system that ServiceNow supports, but there is no role dedicated to Git administration. Reference: Source Control, Source Control Roles

Search branch and merge branches are available features in Studio. Search branch allows you to search for a specific branch name or ID in your Git repository. Merge branches allows you to merge changes from one branch to another, resolving any conflicts that may arise. Push to external source control and push to update set are not available features in Studio. Push to external source control is a feature of Source Control Integration, which is a separate application from Studio. Push to update set is a feature of Update Set Previewer, which is also a separate application from Studio. Reference: Studio, Source Control Integration, Update Set Previewer

https://developer.servicenow.com/dev.do#!/learn/courses/sandiego/app_store_learnv2_learnmore_sandiego_learn_more/app_store_learnv2_learnmore_sandiego_form_and_list_layouts/app_store_learnv2_learnmore_sandiego_what_is_form_designer The Form Designer is a tool that allows you to create and customize forms on the ServiceNow platform. The Form Designer has four main components:
Form layout: The form layout shows the preview of the form and allows you to drag and drop fields, sections, and related lists onto the form. You can also resize, reorder, and delete the elements on the form layout.
Page header: The page header shows the name of the table and the form that you are editing. You can also access the form properties, save the form, and switch to the form view from the page header.
Field navigator: The field navigator shows the list of available fields for the table and allows you to search, filter, and add fields to the form. You can also create new fields and edit existing fields from the field navigator.
Schema map: The schema map is not part of the Form Designer. The schema map is a separate tool that shows the relationships between tables and fields on the platform. You can access the schema map from the System Definition > Tables module or from the context menu of a table.
Reference:
[Form Designer]
[Schema map]