RelNotes entry for New MongoDB collector: CurrentOp (#3155)

* Desc for New MongoDB collector: CurrentOp

* formatting

* feedback from Nurlan

docs/release-notes/2.43.0.md

@@ -15,10 +15,23 @@ This release introduces this and that
 ## Release highlights
 
 
+### New MongoDB collector: CurrentOp
 
+The MongoDB exporter now includes the **CurrentOp** collector, offering visibility into active operations, including the new `mongodb_currentop_query_uptime` metric.
 
+To start the MongoDB exporter with the CurrentOp collector enabled, use the `--enable-all-collectors` flag when adding MongoDB services to your PMM instance:
+
+```sh
+pmm-admin add mongodb --enable-all-collectors ...
+```
+
+Specifying a limit with `--max-collections` for this collector is not necessary.
+
+!!! note "Operation collection limitation"
+    To minimize impact on disk usage, the CurrentOp collector is designed to collect only operations that have been running for longer than 1 minute. This limitation helps focus on potentially problematic long-running operations while keeping data volume manageable.
+
+For more information on MongoDB collectors and metrics, see the [pmm-admin commands documentation](../use/commamds/pmm-admin.md).
 
-![!image](../_images/.png)
 
 ## Improvements