Establishing plant systems for economically viable production of high value biochemicals remains a formidable challenge due to the complexity and interconnectedness of central metabolism, resulting in unpredictable outcomes of metabolic engineering. Marchantia polymorpha, with its haploid-dominant lifecycle and ease of genetic manipulation, has emerged as a promising candidate for exploring plant metabolic engineering. This thesis investigates the potential of M. polymorpha as a testbed for metabolic engineering, focusing on the production of poly-3- hydroxybutyrate (PHB) as a case study. Challenges associated with PHB production such as low substrate availability and complex interactions with endogenous metabolism make it a good target pathway for developing metabolic engineering techniques. Computational modelling of M. polymorpha metabolism guided the identification of promising engineering targets in the cytosol, aiming to enhance PHB production while minimising negative impacts on plant growth. Additionally, the implementation of an optogenetic system enabled inducible PHB biosynthesis, demonstrating different effects on plant growth based on developmental stages. Furthermore, the targeting of PHB-producing enzymes to synthetic biomolecular condensates showed promise, although challenges remain in establishing such condensates in stable Marchantia lines. This study underscores the potential of M. polymorpha as a testbed species for advancing plant metabolic engineering, with implications for sustainable bioproduction systems