Quick action width Increase

1. Create a .css file in your local system along with below code, No need to add any < Style /> keywords

    .slds-modal__container{      width: 80% !important; max-width: 80% !important;     }   

2. Add the above File to Static resources(Public)(Name : CustomModelPopUp) and Refer this file to the lightning component by using ltng Require Attribute.

  <ltng:require styles="{!$Resource.CustomModelPopUp}" />

3. The height is Managed while creating the Quick action.

Reference link:

https://forcepanda.wordpress.com/2019/01/24/how-to-increase-the-width-of-quick-action-modal-popup/