it is hugely annoying when only default needs a change but I still need to fix rest of the states. So much time could be saved with this "rollout switch"

And Done... request to push child design to parent component made:
https://adobexd.uservoice.com/forums/353007-adobe-xd-feature-requests/suggestions/44926339-i-want-to-be-able-to-push-a-design-state-from-one

Oooh this is a great idea. I also want to be able to push a design state from one of its children to the parent. I'm going to create a Feature request for this (if the request doesn't exist already).

This is closely related to actually finishing the basic cross-state inheritance as described in the issue below and elsewhere.
https://adobexd.uservoice.com/forums/353007-adobe-xd-feature-requests/suggestions/41922067-keep-elements-properties-between-states-propagate

Once inheritance is solved in a useful way, the ability to opt elements out of inheritance would be a useful enhancement.

As it stands, components are really just a dangerous distraction. For a project of any size and complexity, you'll be better off communicating states some other way until the XD team finishes this feature.

Edit somthing in the "default state" in a master component with multiple other states - this will destroy all other states.

You will have to start over completely as this will mess up the interactions totally from one state to another and then you have to copy ALOT of things on the rest of canvas if you find of this late in the proces.

FIX ASAP!!