Proposal: KDE Manjaro postinstall script should make this symlink, so the issue is gone. Source: arch wiki.
"Git: ssh_askpass: exec(/usr/lib/ssh/ssh-askpass): No such file or directory
This error is a result of an encrypted ssh-key, and can be solved by installing a dialogue provider like [x11-ssh-askpass] or the alternatives listed there like [ksshaskpass] for KDE.
One thing to note is that for e.g. ksshaskpass you would need to link it from /usr/lib/ssh/ssh-askpass to get VSCode to find it:"
ln /usr/bin/ksshaskpass /usr/lib/ssh/ssh-askpass