I recommend the Roadmaster Rear Anti-Sway Bar, # RM-1209-131, this is a confirmed fit for the 2018 Thor Synergy Motorhome.
Please note the attached product review and installation videos. view full answer...
The best option for electric stabilizing jacks for your motorhome are the Ultra-Fab Power Twin II Electric Stabilizer - 22" Lift # UF39-941707 which will fit if your frame is 42" to 77" wide or the Ultra-Fab Power Twin II Electric Stabilizer with Dual Motors - 30" Lift # UF39-941705 which fits motorhome frames from 48" to 80" wide.
For a tankless water heater we have solutions like the Fogatti part # LSB64FR which has a 41,800 btu output. view full answer...