Orphaned datablocks are those which have either:
* 0 users
* A "fake" user only
In the case of the former, they will be quietly discarded from the file on the next
save + reload. Hence, it is helpful to have a view where you can confirm which ones
fall into this category and might be worth saving.
We also include datablocks with a fake user only so that datablocks given a user
above can have that easily turned off again (in case the user makes a mistake).
Another benefit of showing these is that it become easier to remove fake users from
datablocks you no longer want retained without having to hunt for them.
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