Can WorldServer XML filters support anything other than attributes as SIDs?

Hello WorldServer Community

We are trying to configure SIDs using the Custom XML (Legacy Embedded Content) File Type.

The structure of the file is like this:

<key>SID_ID_here</key>
<string>Translatable content here</string>
...

Is it possible to configure the preceding key value as SID using xpath even if it needs to be done manually on the sdlftsettings file or can only attributes be used as SIDs?

Thanks in advance for any hint.
Andrés Vega