I have attached a photo from a similar system highlighting the setting in question. Malware can immobilize your HP Spectre x360 so it is. This in turn makes laptop turning on trigger battery charging every time laptop is turned on in turn degrading battery sooner.
Also batteries leak some power to circuitry over time, albeit negligible. Use this video to help diagnose the reason behind your Power Adapter Warning or skip to the end to lean how to stop the warning message from being displayed. From there you can disable the warning, apply the change and restart. I have clicked on the DELL BATTERY METER after almost every full charge and disabled battery charging. Cos that up to 5 is used normally for trickle charging SSDs when laptop is off. The warning should be able to be disabled by access the BIOS and navigating to the ‘POST Behavior’ category and then selecting the ‘Adapter Warnings’ item. The Dell-branded power adapter included with your laptop provides 130W of power to the system, and given the Plugable dock provides 60W of power the system is notifying you of the difference. Thank you as well for providing the screenshot of the warning message, that is most helpful. Thanks for posting! We have already responded to the support request you sent to but just to cover all bases and for the benefit of anyone else following this thread I will also post a reply here.