Adding specific items into troubleshooting guide (#88105)

* Update troubleshooting.asciidoc

Adding items into the troubleshooting guide

* Resolve conflicts

* Reorganizes troubleshooting links

Co-authored-by: Abdon Pijpelink <abdon.pijpelink@elastic.co>

docs/reference/troubleshooting.asciidoc

@@ -6,9 +6,45 @@
 This section provides a series of troubleshooting solutions aimed at helping users
 fix problems that an {es} deployment might encounter.
 
-Several troubleshooting issues can be diagnosed using the
+[discrete]
+[[troubleshooting-general]]
+=== General
+* <<fix-common-cluster-issues,Fix common cluster issues>>
+* Several troubleshooting issues can be diagnosed using the
 <<health-api,health API>>.
 
+[discrete]
+[[troubleshooting-data]]
+=== Data
+* <<add-tier,Add a missing tier to the system>>
+* <<allow-all-cluster-allocation,Allow Elasticsearch to allocate the data in the system>>
+* <<allow-all-index-allocation,Allow Elasticsearch to allocate the index>>
+* <<troubleshoot-migrate-to-tiers,Indices mix index allocation filters with data tiers node roles to move through data tiers>>
+* <<increase-tier-capacity,Not enough nodes to allocate all shard replicas>>
+* <<increase-shard-limit,Total number of shards for an index on a single node exceeded>>
+* <<increase-cluster-shard-limit,Total number of shards per node has been reached>>
+* <<corruption-troubleshooting,Troubleshooting data corruption>>
+
+[discrete]
+[[troubleshooting-management]]
+=== Management
+* <<start-ilm,Start index lifecycle management>>
+* <<start-slm,Start snapshot lifecycle management>>
+
+[discrete]
+[[troubleshooting-snapshot]]
+=== Snapshot and restore
+* <<restore-from-snapshot,Restore data from snapshot>>
+* <<add-repository,Multiple deployments writing to the same snapshot repository>>
+
+[discrete]
+[[troubleshooting-others]]
+=== Others
+* <<discovery-troubleshooting,Troubleshooting discovery>>
+* <<monitoring-troubleshooting,Troubleshooting monitoring>>
+* <<transform-troubleshooting,Troubleshooting transforms>>
+* <<watcher-troubleshooting,Troubleshooting Watcher>>
+
 If none of these solutions relate to your issue, you can still get help:
 
 * For users with an active subscription, you can get help in several ways:
@@ -36,23 +72,21 @@ the experts in the community, including people from Elastic.
 
 include::troubleshooting/fix-common-cluster-issues.asciidoc[]
 
-include::troubleshooting/data/increase-shard-limit.asciidoc[]
+include::troubleshooting/data/add-tier.asciidoc[]
 
-include::troubleshooting/data/increase-cluster-shard-limit.asciidoc[]
+include::troubleshooting/data/enable-cluster-allocation.asciidoc[]
 
 include::troubleshooting/data/enable-index-allocation.asciidoc[]
 
-include::troubleshooting/data/enable-cluster-allocation.asciidoc[]
-
 include::troubleshooting/data/data-tiers-mixed-with-node-attr.asciidoc[]
 
-include::troubleshooting/data/add-tier.asciidoc[]
+include::troubleshooting/data/increase-tier-capacity.asciidoc[]
 
-include::troubleshooting/data/diagnose-unassigned-shards.asciidoc[]
+include::troubleshooting/data/increase-shard-limit.asciidoc[]
 
-include::troubleshooting/discovery-issues.asciidoc[]
+include::troubleshooting/data/increase-cluster-shard-limit.asciidoc[]
 
-include::troubleshooting/data/increase-tier-capacity.asciidoc[]
+include::troubleshooting/corruption-issues.asciidoc[]
 
 include::troubleshooting/data/start-ilm.asciidoc[]
 
@@ -62,10 +96,10 @@ include::troubleshooting/data/restore-from-snapshot.asciidoc[]
 
 include::troubleshooting/snapshot/add-repository.asciidoc[]
 
+include::troubleshooting/discovery-issues.asciidoc[]
+
 include::monitoring/troubleshooting.asciidoc[]
 
 include::transform/troubleshooting.asciidoc[leveloffset=+1]
 
-include::../../x-pack/docs/en/watcher/troubleshooting.asciidoc[]
-
-include::troubleshooting/corruption-issues.asciidoc[]
+include::../../x-pack/docs/en/watcher/troubleshooting.asciidoc[]

docs/reference/troubleshooting/fix-common-cluster-issues.asciidoc

@@ -32,10 +32,19 @@ When {es} rejects a request, it stops the operation and returns an error with a
 A backlogged task queue can prevent tasks from completing and put the cluster 
 into an unhealthy state. 
 
+<<diagnose-unassigned-shards,Diagnose unassigned shards>>::
+There are multiple reasons why shards might get unassigned, ranging from 
+misconfigured allocation settings to lack of disk space.
+
+<<cluster-fault-detection-troubleshooting,Troubleshooting an unstable cluster>>::
+A cluster in which nodes leave unexpectedly is unstable and can create several 
+issues.
+
 include::common-issues/disk-usage-exceeded.asciidoc[]
 include::common-issues/circuit-breaker-errors.asciidoc[]
 include::common-issues/high-cpu-usage.asciidoc[]
 include::common-issues/high-jvm-memory-pressure.asciidoc[]
 include::common-issues/red-yellow-cluster-status.asciidoc[]
 include::common-issues/rejected-requests.asciidoc[]
-include::common-issues/task-queue-backlog.asciidoc[]
+include::common-issues/task-queue-backlog.asciidoc[]
+include::common-issues/diagnose-unassigned-shards.asciidoc[]