In WorkFlow, conditional field show
If DocType ="invoice" then SHOW field "Total Invoice".
Show fields depending value of others fields
Thank you for your idea. Right now we are focusing on other topics, so we are not considering this idea for future releases. If the demand for this topic increases, we might add it to future plans.
You can use a condition before the task and then use two different tasks. This seems to be a little more complicated, but structures the workflow easier readable and makes the single tasks less difficult to configure.