I have a pair of 7iDP Transition knee pads that are starting to smell and are in need of a wash. However, I am not totally sure the best course of action for cleaning the pads. Please let me know your suggestions or how you clean your knee pads.
Read the manufacturer's suggestions first.
Then I'd just chuck it all in the washing machine and run a normal cycle.
If there's mud, I'd hose it all off when I wash the bike down before putting in the washing machine.
Once clean, line dry them. A hot-air dryer does more damage to your clothes than anything else.
Washing them by hand with some active detergent should always be the safest, but putting them in the washing machine at low temperatures and low spin rates never harmed my pads.
Maybe you could add some disinfectant or antibacterial additives to compensate for the low temperatures. And if you have a spare bag, e.g. from a full face helmet, those can be used to keep the washing machine from ripping holes in the thin, stretchy fabric of some pads. But thats not a big issue usually. Avoid high temperatures while drying.
This answer feels more like an addition to @Criggie. Would have commented, but I'm lacking reputation.