Not sure if it is still working, but a few years ago I could move Steam OTP to Bitwarden via this 3rd party tool, and it still works nicely for me:
The extracted secrets should work with other authenticators besides BW, but I haven’t tested with anything besides BW.
I dug up the instructions from my notes on how to use it:
"1. Follow the steps linked here Steam Desktop Authenticator. Do not encrypt/add a password (you’re going to delete this after setting it up with Bitwarden, anyway)
2. Look in the maFiles subdirectory where the SDA is installed. One of the files will be named [your_steamID].maFile. Open it.
3. One of the JSON variables will look like: "uri":"otpauth://totp/Steam:your-username?secret=ABCDEFGHIJKLMN1234OPQRSTUVWXYZ4321&issuer=Steam"
4. You want your TOTP entry in Bitwarden to look like: steam://ABCDEFGHIJKLMN1234OPQRSTUVWXYZ4321
5. Get your SteamGuard recovery codes and store them in the notes associated with your Steam login in Bitwarden.
You can confirm it’s working by comparing the value being produced by the desktop authenticator vs Bitwarden."