[Lens] Add more Lens QA doc

docs/user/dashboard/lens.asciidoc

@@ -316,10 +316,16 @@ Each *Layer* in a visualization is associated with an index pattern and mutiple
 You can also change the index pattern for a single *Layer*.
 
 [float]
-[[why-my-field-x-is-missing-from-the-fields-list]]
-===== Why is my field X missing from the fields list?
+[[why-my-field-is-missing-from-the-fields-list]]
+===== Why is my field missing from the fields list?
 
-*Lens* does not support the visualization of full-text fields, therefore it is not showing them in the data summary.
+Fields do not appear in the *Available fields* in the following scenarios:
+* The field is a full-text field.
+* The field is a `geo_point` field
+* The field is a `flattened` field.
+* The field is a `object` field.
+
+Verify if the field appears in the *Empty fields* list. *Lens* uses heuristics to determine if the fields contain values. For sparse data sets, the heuristics are less precise.
 
 [float]
 [[how-to-handle-gaps-in-time-series-visualizations]]
@@ -370,3 +376,9 @@ Here's a short list of few different aspects to check:
 ** If a custom `Number` configuration is used, check that the color stop values are covering the current data range.
 
 ** If a `Percent` configuration is used, and the data range changes, the colors displayed are affected.
+
+[float]
+[[is-it-possible-to-show-icons-in-datatable]]
+===== Is it possible to display icons in data tables?
+
+You can display icons with <<managing-index-patterns, field formatter>> in data tables.