I need automatically sync my passwords, stored in kwallet, with 2 computers.
How can I do this?

Use the file syncing tool like dropbox is dangerous - I can lost some data.
For example, I store login 'petya' in kwallet on first computer and some time later - store 'vasya' on second computer, before file syncing is started. And after sync finish I lost the login 'petya' from kwallet file.

Does exist some other methods to sync the data in kwallet?
Maybe some cli command to merge 2 kwl files?

Kwallet graphical tool have an option "Merge Wallet" that works good.
But can I initialize merge process from cli?
kwalletcli tool didn't have the merge option...

You will probably need to file a feature request at bugs.kde.org to get merge wallet available at the cli.

Thank's for idea, I have create it: https://bugs.kde.org/show_bug.cgi?id=234309
But I hope that any can tell me some other method to sync, because waiting when wishlist was completed will be so long
Maybe exist any way to do automatically list of my actions with application kwalletmanager (select menu item, file, press "open", etc) via some software?

As far as I know, there isn't a way to script actions using X... however it does have a debug interface which allows applications to send false mouse / keyboard events, thus it is possible.

I use the way with manually syncing kdewallet.kwl file between computers already long time, and sometimes got problems with overwriting cloud changes with local, especially when I setup new KDE account on device. After next time when this way delete (overwrite) all my password database via empty file, my patience is over!

I'm tired of waiting when native sync via ksecretsservice and secretsync will be implemented, and fill issue on KWalletManager bug tracker: https://bugs.kde.org/show_bug.cgi?id=403648

Please join to it and vote for quicker fix kwallet sync problem via manually syncing kwallet.kwl file!