Update Group Import/Export docs

doc/api/group_import_export.md

 # Group Import/Export API
 
-> Introduced in GitLab 12.8 as an experimental feature. May change in future releases.
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/20353) in GitLab 12.8 as an experimental feature. May change in future releases.
 
-Group Import/Export functionality allows to export group structure and import it at a new location.
-Used in combination with [Project Import/Export](project_import_export.md) it allows you to preserve connections with group level relations
-(e.g. a connection between a project issue and group epic).
+Group Import/Export allows you to export group structure and import it to a new location.
+When used with [Project Import/Export](project_import_export.md), you can preserve connections with
+group-level relationships, such as connections between project issues and group epics.
 
-Group Export includes:
+Group exports include the following:
 
-1. Group Milestones
-1. Group Boards
-1. Group Labels
-1. Group Badges
-1. Group Members
-1. Sub-groups (each sub-group includes all data above)
+- Group milestones
+- Group boards
+- Group labels
+- Group badges
+- Group members
+- Sub-groups. Each sub-group includes all data above
 
 ## Schedule new export
 
@@ -58,7 +58,11 @@ ls *export.tar.gz
 2020-12-05_22-11-148_namespace_export.tar.gz
 ```
 
-Time spent on exporting a group may vary depending on a size of the group. Export download endpoint will return exported archive once it is available. 404 is returned otherwise.
+Time spent on exporting a group may vary depending on a size of the group. This endpoint
+returns either:
+
+- The exported archive (when available)
+- A 404 message
 
 ## Import a file
 
@@ -81,3 +85,12 @@ by `@`. For example:
 ```shell
 curl --request POST --header "PRIVATE-TOKEN: <your_access_token>" --form "name=imported-group" --form "path=imported-group" --form "file=@/path/to/file" https://gitlab.example.com/api/v4/groups/import
 ```
+
+## Important notes
+
+Note the following:
+
+- To preserve group-level relationships from imported projects, run Group Import/Export first,
+  to allow project imports into the desired group structure.
+- Imported groups are given a `private` visibility level, unless imported into a parent group.
+- If imported into a parent group, subgroups will inherit a similar level of visibility, unless otherwise restricted.

doc/user/project/settings/import_export.md

@@ -12,6 +12,7 @@ See also:
 
 - [Project import/export API](../../../api/project_import_export.md)
 - [Project import/export administration rake tasks](../../../administration/raketasks/project_import_export.md) **(CORE ONLY)**
+- [Group import/export API](../../../api/group_import_export.md)
 
 To set up a project import/export: