LDAC should be an option in the XM4s settings under Bluetooth devices. It might not show up if multi device pairing is enabled, which you probably need to have their headphones app to disable.
In the same app under Sound there's an option to prioritize sound quality that should make it auto select the LDAC codec.
I'm pretty sure all the settings are saved to the actual headphones so you can optionally uninstall or disable the app once everything is how you want it.
If you're talking about the developer setting to force the highest LDAC bitrate, enabling developer options is one way to do it. I used to do that but it was unreliable and would keep resetting to the default setting. The Sony Music Center app(separate app from Headphones Connect) has an option under "Bluetooth output" that seems to keep it at the higher bitrate setting: "prioritize LDAC" once again makes it use LDAC if available, and "Priority on sound quality" should make it select the highest bitrate.