  We have developed an innovative workflow, STEP-0D, within the OMFIT
integrated modelling framework. Through systematic validation against the
International Tokamak Physics Activity (ITPA) global H-mode confinement
database, we demonstrated that STEP-0D, on average, predicts the energy
confinement time with a mean relative error (MRE) of less than 19%. Moreover,
this workflow showed promising potential in predicting plasmas for proposed
fusion reactors such as ARC, EU-DEMO, and CFETR, indicating moderate H-factors
between 0.9 and 1.2. STEP-0D allows theory-based prediction of tokamak
scenarios, beginning with zero-dimensional (0D) quantities. The workflow
initiates with the PRO-create module, generating physically consistent plasma
profiles and equilibrium using the same 0D quantities as the IPB98(y,2)
confinement scaling. This sets the starting point for the STEP (Stability,
Transport, Equilibrium, and Pedestal) module, which further iterates between
theory-based physics models of equilibrium, core transport, and pedestal to
yield a self-consistent solution. Given these attributes, STEP-0D not only
improves the accuracy of predicting plasma performance but also provides a path
towards a novel fusion power plant (FPP) design workflow. When integrated with
engineering and costing models within an optimization, this new approach could
eliminate the iterative reconciliation between plasma models of varying
fidelity. This potential for a more efficient design process underpins
STEP-0D's significant contribution to future fusion power plant development.
