which is the best way to switch from a full node wallet to a light one - without losing old addresses of course?
If you only have public assets (bytes for instance) then the seed is enough. Save it, uninstall your full wallet, install a light wallet and restore using the seed. You'll get your addresses with their public assets' balances.
If you have private assets (blackbytes for instance) then you'll have to wait for your full wallet to sync, install a(n intermediary) light wallet elsewhere (a different user will do if you want to stay on the same machine) and transfer your blackbytes then your bytes to it. If you want your old addresses back, then after emptying your full wallet, uninstall it, install a light one and recover from the seed. You'll then have to send your assets from your intermediary light wallet to your newly installed light wallet (always leave sending the bytes at the end, because you'll need them for fees to send everything else).
I went through the process as suggested but I had to find out that this is simply not possible if you have multisig addresses in your app. While trying to recover from the seed I've got a message of "invalid seed", I guess because there were multisig addresses inside. So it really seems that if you want to switch from a full node wallet to a light one and you are having multisig addresses you cannot do it without losing all your old addresses. It is a pity, because one should never renounce to old addresses just in case you find out you still need some. However, keeping the full node on PC is a constant pain one would rather get rid of. So the only choice not to lose the old addresses while switching to a lite node is to keep forever ALSO a backup of your (now emptied) fullnode wallet, to be restored just in case of need.
I hope my experience can be useful to others with my same needs.
