Is it possible to create a watching only wallet in bitcoin core for a given wallet address? If yes, can you explain to me how to do it?
Yes, this has been made possible ages ago, see
https://www.reddit.com/r/Bitcoin/comments/2a222h/support_for_watchonly_addresses_merged_into/I'm not entirely sure how you can add one in core speficically, but it shouldn't be too difficult. All you do is add an adress basically.
Try something like this here?
https://www.reddit.com/r/Bitcoin/comments/3ewig4/really_like_the_watch_only_functionality_in/The "importaddress" RPC adds an address or pubkey script to the wallet without the associated private key, allowing you to watch for transactions affecting that address or pubkey script without being able to spend any of its outputs.
https://bitcoin.org/en/glossary/watch-only-addressIt seems that some people have difficulties with it.
See;
In the console just use:
"importaddress" and use no rescan. After having imported all addresses, rescan to get the balances right. In the QT window the watch-only addresses will popup with their respective balances in a separate area. To see the balances after the rescan, you need to run a full node with the full block chain. If you run a pruned node you will have to reload the whole block chain again. This is not really necessary if you are not interested in historical transactions and only in the final balance because the UTXO set is enough. I made a github issue of that but it hasn't been implemented yet.
https://www.reddit.com/r/Bitcoin/comments/5z35nm/watchonly_wallet_in_bitcoin_core_qt/
