diff --git a/inst/shiny/functions/mapping_selectize_inputs.R b/inst/shiny/functions/mapping_selectize_inputs.R
index b4f67a82..ac5c1a01 100644
--- a/inst/shiny/functions/mapping_selectize_inputs.R
+++ b/inst/shiny/functions/mapping_selectize_inputs.R
@@ -13,12 +13,33 @@
 #' @return None. This function updates the selectize inputs in the Shiny session.
 
 update_selectize_inputs <- function(session, input_ids, column_names, manual_units, desired_order) {
+
+  # Define the desired columns for Grouping_Variables
+  desired_grouping_columns <- c("TRTA", "TRTAN", "ACTARM", "TRT01A",
+                                "TRT01P", "AGE", "RACE", "SEX", "GROUP")
+
   for (input_id in input_ids) {
+    # Remove the "select_" prefix to get the actual column name
     column_name <- sub("select_", "", input_id)
-    selected_value <- if (column_name %in% column_names) column_name else NULL
+    # Determine the selected value(s) based on the column name
+    if (column_name == "Grouping_Variables") {
+      # Find which desired grouping columns are present
+      selected_values <- intersect(desired_grouping_columns, column_names)
+
+      # If none are present, set to NULL
+      if (length(selected_values) == 0) {
+        selected_values <- NULL
+      }
+    } else {
+      # For other columns, use basic logic
+      selected_values <- if (column_name %in% column_names) column_name else NULL
+    }
+    # Update the Selectize input with the new choices and selected values
     updateSelectizeInput(
-      session, input_id, choices = c("Select Column" = "", column_names),
-      selected = selected_value
+      session,
+      input_id,
+      choices = c("Select Column" = "", column_names),
+      selected = selected_values
     )
   }
 
@@ -42,13 +63,9 @@ update_selectize_inputs <- function(session, input_ids, column_names, manual_uni
     updateSelectizeInput(
       session, input_id,
       choices = special_cases[[input_id]],
-      selected = if (sub("select_", "", input_id)
-                     %in% column_names) sub("select_", "", input_id) else NULL
+      selected =
+        if (sub("select_", "", input_id) %in% column_names)
+          sub("select_", "", input_id) else NULL
     )
   }
-
-  updateSelectizeInput(
-    session, "select_Grouping_Variables",
-    choices = setdiff(column_names, desired_order)
-  )
 }
diff --git a/inst/shiny/modules/column_mapping.R b/inst/shiny/modules/column_mapping.R
index 827f1812..386f06e2 100644
--- a/inst/shiny/modules/column_mapping.R
+++ b/inst/shiny/modules/column_mapping.R
@@ -243,7 +243,7 @@ column_mapping_server <- function(id, data, manual_units, on_submit) {
 
     # Define the required columns and group them into categories
     column_groups <- list(
-      "Group Identifiers" = c("STUDYID", "USUBJID", "Grouping Variables"),
+      "Group Identifiers" = c("STUDYID", "USUBJID", "Grouping_Variables"),
       "Sample Variables" = c("ANALYTE", "PCSPEC", "ROUTE", "AVAL"),
       "Dose Variables" = c("DOSNO", "DOSEA", "ADOSEDUR"),
       "Time Variables" = c("AFRLT", "ARRLT", "NFRLT", "NRRLT"),
@@ -299,12 +299,12 @@ column_mapping_server <- function(id, data, manual_units, on_submit) {
         return()
       }
 
-      # Extract and store the "Grouping Variables" column
+      # Extract and store the "Grouping_Variables" column
       grouping_variables(input$select_Grouping_Variables)
 
-      # Remove "Grouping Variables" from selected columns to prevent renaming
+      # Remove "Grouping_Variables" from selected columns to prevent renaming
       selected_cols[["Group Identifiers"]] <- selected_cols[["Group Identifiers"]][
-        names(selected_cols[["Group Identifiers"]]) != "Grouping Variables"
+        names(selected_cols[["Group Identifiers"]]) != "Grouping_Variables"
       ]
 
       # Rename columns