How to substitute username/connection string in SSH config?

Question

I'm trying to configure SSH to log into multiple hosts behind a CyberArk PSM SSH proxy.

I'm using OpenSSH v. 9.4.

I can connect directly like this:

ssh -i <key> <user>@<cybearkuser>%<domain>@<remotehost>@<proxyaddress>

The only variable here is remotehost, so I want to configure SSH to automatically replace it in the long connection string, when I just type ssh remotehost.

I first made my SSH config like so:

Host abc-*remotehost
    Hostname user@user%%domain.com@%[email protected]
    IdentityFile ~/.ssh/key

Note that %h expands to the host, and %% is just a regular %.

But now, when I just do ssh abc-123.remotehost, it seems SSH interprets the whole line as a host (understandably), and complains it cannot resolve it. It correctly substituted the hostname into the long string, though.

I assume everything before the final @ is supposed to be the SSH username, so I thought I could just do this:

Host abc-*remotehost
    Hostname proxy.domain.com
    User user@user%%domain.com@%h
    IdentityFile ~/.ssh/key

But that doesn't work, as these substitution tokens only work on specific keywords, and not User (man page).

Note that if I just put the whole <user>@<cybearkuser>%<domain>@<remotehost> part in statically as User, it works fine, but I really want to substitute it to avoid repeating this for 30+ hosts.

Is there some other trick I can try?