That string of characters after dev-container+ is an ascii path to your dev container folder encoded in hexadecimal.
To open a folder in a container you can use the following style command:
code --folder-uri=vscode-remote://dev-container%2B{path-in-hex}/{path-inside-container}
For example to open the folder /workspaces/test
in the development container located in /Users/jkells/projects/vscode-devcontainer
I use the following CLI command.
code --folder-uri=vscode-remote://dev-container%2B2f55736572732f6a6b656c6c732f70726f6a656374732f7673636f64652d646576636f6e7461696e6572/workspaces/test
To convert the string /Users/jkells/projects/vscode-devcontainer
into the hexadecimal 2f55736572732f6a6b656c6c732f70726f6a656374732f7673636f64652d646576636f6e7461696e6572
you can use the following command
printf /Users/jkells/projects/vscode-devcontainer | od -A n -t x1 | tr -d '[\n\t ]'