Home Business - Entering Expenses

Hi - I work as a psychologist and, as I do the majority of my work virtually, I work out of my home (no other office).  Historically, we have written off 20% of home expenses that are also used for the running of my practice (e.g. utilities, some home repair, etc...) as that is the percentage of square footage of the home used for business purposes.  This will be my first year using Quickbooks Online and wondering if there is an automated way of entering the expense (a receipt for something related to home repair, for example) and Quickbooks automatically calculating the 20% towards the business.  The expense is sometimes being paid out of a personal account rather than a business account yet may also be paid for out of a business account. Can categories be created that automatically accomplish this task or do these expenses need to be entered as journal entries in the Chart of Accounts?  Thanks!