xpWeight enables you to apply a weighting to any modifier or modifiers.

This is an additional 'strength' control, which enables you to change the strength depending on parameters such as particle age.

General tab

xpWeight General tab.

Enabled

Checking this box enables the xpWeight modifier.

Mode

Set at Independent by default.

You can change this to Action-Controlled.

Independent Mode

In this mode, particles will be affected if they come into the field of effect of the modifier.

Action-Controlled Mode

When in the Action-Controlled Mode setting, the modifier will only act on a particle when told to do so by an action.

Operation

Set as Standard, by default.

With Operation set to Standard, every modifier added to the Modifiers list has a Weight slider, that you can adjust to control exactly how strong the effect of that modifier is, in conjunction with the other modifiers.