Optical true time delay line (OTTDL) is essential for signal processing in microwave photonics (MWP) and optical communications. This study presents an index-variable OTTDL based on forty subwavelength grating (SWG) waveguides fabricated on a silicon-on-insulator. Numerical simulations of the resulting time delays in the SWG waveguide-based OTTDL are presented for various MWP applications. Simulation results demonstrate that: the structure enables a microwave photonic filter with discrete frequency tuning and reconfigurability; it facilitates discrete beam-steering angle tuning in phased array antennas without introducing beam squinting effects; it is suitable for implementing multi-cavity Vernier and unbalanced dual-cavity optoelectronic oscillators, achieving discrete oscillation frequency tuning while characterizing corresponding oscillation spectra and phase noise performance. This work provides a viable solution for high-performance, compact integrated MWP signal processing.