Save GPX downloads an export to your device. Keep that file somewhere you can find again, with a name that identifies the circuit and layout.
A saved cloud track and a downloaded GPX serve different purposes: use My Tracks to return to your editable document, and keep exports for the workflows that require them.
Do not assume every receiving tool supports every definition or metadata field. If another tool rejects an export, report its name, the format expected and the exact error.