To keep one's local reputation if changing the data directory an export/import feature for the onion address would be nice to have. It simply requires hostname and private_key files from the hidden service directory.
Where in UI do we want to have this functionality (Settings->Network info)?
In the Tor settings dialog at Settings->Network info->Open Tor settings.
Would it make sense to merge this with issue #1056 ?
This is what I have in mind:

@fotispap Thanks!
I would use the term private key for what is exported/imported instead of onion address. Renew onion address is ok, but import/export priv key...
I would also not add it to the Tor settings as that is shown automatically at connection problems. Better to add a button in the network settings for renewing the onion address. Then show the details in a new popup.
It is important to explain the user that he can do that only if he has no offers/trades/disputes open and the he will lose his local reputation (those he has traded with will not see him as the same node and therefore the number of trades displayed in the avatar will be not valid anymore).
I also is important to check for open offers/trades/disputes and only allow then the renewal.
Such checks are already partially in place for emptying the wallet for instance...
Sorry for disappearing! I am not sure if assigning @freimair means he plans to work on this? I am working on a version incorporating @ManfredKarrer suggestions. I decided to implement the functionality first and worry about the GUI part later. I am hoping to have a pull request ready next week.
@fotispap Ah cool. If you work alreay on it then please go on. @freimair was just jumping in here as it was not clear that someone else works on it.
alright, I leave it to you then
i guess you are onto #1056 as well?
Thanks freimair! Yes, I thought it made sense implementing the as one, since they are very similar functionalities. I will try to get a pull request soon, and looking forward to your feedback.
@fotispap Do you plan on getting this done still? if not, I would take over and get it done.
how about:

Exact labels and titles are to be discussed of course...
I would use "key" instead if "ID" or "address".
It requires some checks if open offer, trades or disputes are there and if so tell the user that he has to wait until those are closed (or close offers).
hm, I was thinking whether we should change "My onion address" to "My ID" because what else is that highly cryptic string of characters to a user. Having an ID is quite common in today's interwebs, why burden the user with this "onion address" thing, whatever that might be.
ad checks: of course.
ad feature: I plan on forcing a restart of the app after a renewal or import. Because