## 1 Introduction  
In recent years, technological advancements and policy directives in the European Union (EU) [1] and the United States of America [2] have led to a significant increase in the number of Distributed Energy Resources (DER) that are primarily connected to the energy grid [3]. Therefore, the traditional energy consumers have been transformed into prosumers, i.e., active entities of the energy market that simultaneously consume, produce and share energy, depending on the regulatory framework, the weather and the operating conditions [4]. Prosumers may own multiple energy assets, primarily small-scale DERs for energy generation, and batteries or Electric Vehicles (EVs) for energy storage [5]. These trends reshape the conventional and centralized power system and eventually disrupt the existing energy system. In this emerging landscape, the power system must undergo structural changes to adapt and leverage the benefits of Internet of Things (IoT) technologies, digitalization, and decarbonization policies. The edge grid is a structural component of the power system; thus, the concepts of Transactive Energy System (TES) and Local Energy Market (LEM) are considered novel solutions that enable energy exchange between prosumers, increase the power system's efficiency, and reliability, and support the coordination between DERs [6]. Financial and engineering advancements are embraced by TES and LEM, and they form an integral part of the hierarchical energy marketplace, which includes wholesale, retail, and local markets. Inevitably, the solutions of TES and LEM offer incentives for participation for all stakeholders and maximize the social welfare in the energy market. The exponential growth of computational power and IoT has created a strong technological infrastructure for collecting, transmitting, and processing data in a reliable, efficient, and cost-effective manner. In this context, the concept of Digital Twin (DT), i.e., virtual representations of physical entities that encompass the most discriminative characteristics of the corresponding entity, has attracted the attention of researchers and the industry. Bidirectional and automatic data flow between the physical and virtual entities are used by DTs to produce predictive analytics, perform actions and support informed decisions. In the power sector, DTs are considered promising solutions for sustainability, demand side management, control of energy assets, reliable energy distribution and monitoring of energy grid operations [7]. As flexibility can be obtained either at the residential or community level, this work focuses on residential flexibility, which is then procured to the external grid through LEM. Controlling Heating, Ventilation and Air Conditioning (HVAC) systems based on consumers' thermal comfort tolerance, scheduling household appliances and EV charging are the typical ways to obtain residential flexibility. Based on the consumer's preferences, designated flexible loads are activated at optimal intervals during the desired time window to minimize energy costs. Moreover, by allowing the consumer to specify the subjective intensity of importance for each flexible load, prioritized Demand Response (DR) scheduling can be implemented. As residential flexibility is becoming critical for power systems and is now at the forefront of the energy market, LEMs are acting as a catalyst in procuring residential flexibility and empowering small RES owners [8]. LEMs simplify and accelerate this process, enabling energy consumers at the edge of the grid to evolve from passive entities to active integral energy market actors. Despite the fact that LEMs expedite consumers' participation in the energy market, prosumers' involvement will not be materialized as long as their market engagement is conducted in a complicated way, limiting the interest on LEM and leading to potential depreciation and eventually failure. Apparently, a seamless and consumer-friendly way of market engagement is a decisive factor for LEM's success.