Is there any updated documentation on the label sync plugin? I found instructions here:
https://bitcointalk.org/index.php?topic=154144.0 but that seems to be for an older version of the plugin. The help icon references this page
https://github.com/maran/electrum-sync-server but doesn't talk about usage of the client. Do I just click "force upload" on the computer that has my labels and then "force download" on my watching only wallets, without signing up for any account or entering an API key?
As far as i used it yes. The only thing needed is the key and your wallet is recognized and the labels attached to the addresses and transactions are stored and recovered.
Though its of course that your labels are stored at a server, so centralized risk. I would prefer having the possibility to specify a file on my computer, i would store it in a cloud directory, and let my labels sync there. I would at least avoid that additional risk. I mean server owners has to give out the details when asked, especially in the US.
Saying that... the feature saved my labels often since the electrum database not seldom loses labels.