[Discover] Restore context documentation (#90784)

Co-authored-by: gchaps <33642766+gchaps@users.noreply.github.com>

docs/discover/context.asciidoc

@@ -0,0 +1,60 @@
+[[discover-document-context]]
+== View surrounding documents
+
+Once you've narrowed your search to a specific event in *Discover*,
+you can inspect the documents that occurred
+immediately before and after the event.
+To view the surrounding documents, your index pattern must contain time-based events.
+
+. In the document table, click the expand icon (>).
+. Click *View surrounding documents.*
++
+In the context view, documents are sorted by the time field specified in the index pattern
+and displayed using the same set of columns as the *Discover* view from which
+the context was opened. The anchor document is highlighted in blue.
++
+[role="screenshot"]
+image::images/discover-context.png[Image showing context view feature, with anchor documents highlighted in blue]
++
+The filters you applied in *Discover* are carried over to the context view. Pinned 
+filters remain active, while normal filters are copied in a disabled state.
+
++
+[role="screenshot"]
+image::images/discover-context-filters-inactive.png[Filter in context view]
+
+. To find the documents of interest, add filters.
+
+. To increase the number of documents that surround the anchor document, click *Load*.
+By default, five documents are added with each click.
++
+[role="screenshot"]
+image::images/discover-context-load-newer-documents.png[Load button and the number of documents to load]
+
+
+[float]
+[[configure-context-ContextView]]
+=== Configure the context view
+
+Configure the appearance and behavior in *Advanced Settings*.
+
+. Open the main menu, then click *Stack Management > Advanced Settings*.
+. Search for `context`, then edit the settings.
++
+[horizontal]
+`context:defaultSize`:: The number of documents to display by default.
+`context:step`:: The default number of documents to load with each button click. The default is 5.
+`context:tieBreakerFields`:: The field to use for tiebreaking in case of equal time field values.
+The default is the `_doc` field.
++
+You can enter a comma-separated list of field
+names, which is checked in sequence for suitability when a context is
+displayed. The first suitable field is used as the tiebreaking
+field. A field is suitable if the field exists and is sortable in the index
+pattern the context is based on.
++
+Although not required, it is recommended to only
+use fields that have {ref}/doc-values.html[doc values] enabled to achieve
+good performance and avoid unnecessary {ref}/modules-fielddata.html[field
+data] usage. Common examples for suitable fields include log line numbers,
+monotonically increasing counters and high-precision timestamps.

docs/user/discover.asciidoc

@@ -161,7 +161,8 @@ image:images/document-table-expanded.png[Table view with document expanded]
 . Scan through the fields and their values. If you find a field of interest,
 hover of its name for filters and other controls.
 
-. To view documents that occurred before or after the event you are looking at, click **View surrounding documents**.
+. To view documents that occurred before or after the event you are looking at, click
+<<discover-document-context, View surrounding documents>>.
 
 . For direct access to a particular document, click **View single document**.
 +
@@ -218,4 +219,6 @@ include::{kib-repo-dir}/discover/set-time-filter.asciidoc[]
 
 include::{kib-repo-dir}/discover/search.asciidoc[]
 
+include::{kib-repo-dir}/discover/context.asciidoc[]
+
 include::{kib-repo-dir}/discover/search-for-relevance.asciidoc[]