The starting conditions have a checkbox that allows you to disable them by unchecking Enable event.

You can export workflows to local file which can be imported as a new workflow (similar to an on-prem system) and I was asked to create a copy of a workflow for a support case. Therefore I exported the production workflow in order to import as a new workflow (there is no copy button)

You can then import workflow files as new workflows.

However later the customer asked if we disabled a starting rule on their production workflow and we did not, but it was disabled by someone.

I found that if you import a workflow file, the workflow which the file was created from gets it's starting rules automatically disabled without anyone touching it.

When you check the starting rules, the Enable event checkbox is unchecked.

This is a huge problem as this should never disable itself unless someone asks for that to be done, many instances were missed because it was disabled for a period of time.

Submitted a support case: 248170