Description of problem:
This is most probably a long standing problem, but we "discovered" it today with Vratislav Podzimek. Any actions done in the guided partitioning screen cannot be reverted, *once you left the reclaim dialog*. You can't come back to that screen and re-adjust it. That means:

* If you mark a partition for deletion (e.g. by mistake), you can't reset it to "preserve". The partition is no longer displayed in the reclaim dialog.
* If you shrink a partition too much, you can't "unshrink it/enlarge it", you can only shrink it more.

Obviously, the desirable solution would be that the reclaim dialog would display all partitions every time it is opened, including "pending operations". So if I marked a partition for deletion, it should be shown as such the next time I open the reclaim dialog, so that I could switch it back to "preserve". Similarly for partitions marked to be shrunk, I should see the full size of the partition, and I should be able to move the slider both left and right to shrink it more or less.

These changes would probably be too difficult for upcoming F21 release. Vratislav experimented with at least adding a Reset All button, similarly to what custom partition screen contains, so that users can use to reset everything to an on-disk state and therefore fix their possible mistakes this way. Might be a good idea until the proper fix is implemented (provided you agree with me on the way this should work).

Version-Release number of selected component (if applicable):
anaconda-21.48.16-1.fc21.x86_64
python-blivet-0.61.10-1.fc21.noarch
https://vpodzime.fedorapeople.org/ultimate_f21_updates.img applied

How reproducible:
always

Steps to Reproduce:
1. enter guided part
2a. mark a partition for deletion, confirm
3a. realize your mistake
4a. enter guided part again, try to undelete the partition - it's nowhere to be found

2b. mark a partition to be shrunk, confirm
3b. realize your mistake
4b. enter guided part again, try to shrink the partition less - it's not posssible, only shrink more

Additional info:
See video!