How to get Thunderbird attachments as read/write...

This has been bugging me for years now... ( I guess ).
When I double click e.g. an OpenOffice attachment in Thunderbird, the document is then opened as read-only in OpenOffice.

There's 1000+1 reasons on the web why this is a) intended and b) good... but I still did not like it.

Some (short) analysis revealed, that Thunderbird is actually setting the read-only attribute of the attachment, so OpenOffice was not to blame.
Easy to google from that and find a really good tip here:

One has to set the configuration value browser.helperApps.deleteTempFileOnExit to false [1]

E voila... Works fine now.
No unintended side effects so far.
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[1] you might have to create it...