[DOC] Painless lab enable/disable flag (elastic#95392)

* [DOC] Painless lab enable/disable flag

* Update docs/settings/dev-settings.asciidoc

* Update docs/settings/dev-settings.asciidoc

Co-authored-by: Kaarina Tungseth <kaarina.tungseth@elastic.co>
Co-authored-by: Kibana Machine <42973632+kibanamachine@users.noreply.github.com>

docs/settings/dev-settings.asciidoc

@@ -29,3 +29,14 @@ They are enabled by default.
   | Set to `true` to enable the <<xpack-profiler,{searchprofiler}>>. Defaults to `true`.
 
 |===
+
+[float]
+[[painless_lab-settings]]
+==== Painless Lab settings
+
+[cols="2*<"]
+|===
+| `xpack.painless_lab.enabled`
+  | When set to `true`, enables the <<painlesslab, Painless Lab>>. Defaults to `true`.
+
+|===