Percentage transaction splitting

[kiwibloke]

I am running Version: 1.8.0 64-bit on Windows 10.
My goal for UK tax reporting is to be able to automatically split various expenses by percentage between the following categories:
Home: Subcategory
Business 1:Subcategory
Business 2:Subcategory

For example, the total monthly energy transaction for the house is split into three categories:
Home: Energy bill 33%
Business 1: Energy bill 33%
Business 2: Energy bill 33%

Please note I have many other splitting examples where I need to split a transaction equally into three categories or two categories.

The amount each month for energy usually varies, therefore an automatic percentage calculation would be required whenever I import the monthly bank CSV statement.
I cannot see a current feature in transaction splitting that allows me to do this unless I am missing something?