Example of creating/updating StringTables

GenerateStringTables.cs

using System.Linq;
using UnityEditor;
using UnityEditor.Localization;
using UnityEngine;
using UnityEngine.Localization.Tables;

public class GenerateStringTables : ScriptableWizard
{
    public TextAsset jsonFile;
    public string tableCollectionName = "My Strings";

    [MenuItem("Localization Example/Import Json")]
    static void CreateWizard()
    {
        DisplayWizard<GenerateStringTables>("Import");
    }

    static AssetTableCollection FindStringTableCollection(string name)
    {
        var allCollections = LocalizationEditorSettings.GetAssetTablesCollection<StringTable>();
        return allCollections.FirstOrDefault(col => col.TableName == name);
    }

    void OnWizardCreate()
    {
        // You will need to create the StringTables in the editor as we have not exposed `CreateAssetTableCollection`.
        var foundCollection = FindStringTableCollection(tableCollectionName);
        if (foundCollection == null)
        {
            Debug.LogError($"Please create a StringTable collection with the namme `{tableCollectionName}`");
            return;
        }

        // TODO: Load your Json data here

        foreach(var table in foundCollection.Tables)
        {
            StringTable stringTable = table as StringTable;

            // Assuming you have multiple json files in the form "de.json".
            // Find the json file by using:
            var languageCode = stringTable.LocaleIdentifier.Code; // For german this would be `de`.

            /*
            foreach(var entry in yourJsonFile)
            {
                stringTable.AddEntry(entry.Name, entry.TranslatedValue);
            }
            */

            // Mark the table dirty
            EditorUtility.SetDirty(table);
        }
    }
}