F=ma
Force is equal to Mass x Acceleration

Power = Weight x Speed (simple terms for boxing)

Without sacrificing the main role of the jab, you either need to gain weight or increase speed.

A jab is never going to KO someone so forget about power.

You want to improve your jab, improve your speed
You want to increase your power increase your speed

There is no secret formula, just jab fast, do not tense your muscles until impact, quit trying to get KO power with the jab, focus on speed, twice the speed hurts twice as much.

Do not try and telegraph a jab or get huge power from a jab.

Jab's effectiveness comes from its speed not its power.

Imagine taking 50 straight lefts/jabs at huge power.
Now Imagine getting hit quickly in succession with 50 lightning fast jabs.
Yes the later will hurt much more and stop you from countering.

Think less about power and more about speed, jab is not a KO punch, it is a range punch.