I think it would be really useful if workflow tasks could be enabled/disabled.
This would help both in the design phase, as well as for troubleshooting workflows, as tasks could be bypassed/skipped without altering the actual workflow structure.
Additionally, when a workflow task is disabled maybe we could have a "default action" task setting, so that even when (for example) an approval task is disabled, the workflow wouldn't "stall" as we could choose to automatically follow the "Approved" path/route of the workflow.
Finally, and closing the whole workflow design/save/test cycle, it would be great if workflows could be started from within the workflow designer, for example by defining a doc number in the workflow settings to run the workflow against. (similarly to how it's done in the REST task)
The process of modifying, saving and having to leave the Solution Designer to run/test workflows feels like too many steps/clicks, something that if improved could save us a ton of time, especially in projects with many workflows.