Cosmological simulations indicate that nearly half of the baryons in the nearby Universe are in the warm-hot intergalactic medium (WHIM) phase, with about half of which residing in cosmic filaments connecting galaxy clusters. Recent observational studies using stacked survey data and deep exposures of galaxy cluster outskirts have detected soft X-ray excess associated with optically identified filaments. However, the physical characteristics of WHIM in filaments remain largely undetermined due to the lack of direct spectral diagnostics of individual targets, limited by the spectral resolution of current instruments in the soft X-ray band. We aim to select appropriate targets for WHIM characterization through pointing observations with the future HUBS mission, which is designed with eV level energy resolution in the 0.1-2.0keV band and a 1 square degree field-of-view, complementing other planned microcalorimetry missions such as Athena.We built a sample of 1577 inter-cluster filaments based on the first eROSITA All-Sky Survey (eRASS1) supercluster catalog and estimated their soft X-ray emission. Their modeled geometrical properties and oxygen line intensities were used to select candidate targets for HUBS observations.Four inter-cluster filaments were selected as the most appropriated candidates. By simulating and analyzing their mock observations, we demonstrated that with 200ks HUBS exposure for each candidate, the gas properties of individual filaments can be accurately determined, with the temperature constrained to +/-0.01keV, metallicity constrained to <=+/-0.03 solar and density constrained to <+/-10%. Elemental abundance of O, Ne, Mg, and Fe can be measured separately, providing unprecedented insights into the chemical history of the filament gas. We also showed that direct mapping of the WHIM distribution is promising with narrow- band imaging of the O VIII line.Our work forecasts that next-generation X-ray missions such as HUBS will provide substantial improvement in our understanding of the physical status and evolution history of the diffuse WHIM gas in cosmic large-scale structure.