I would just pull out the longer cable from my backpack. Or use the power bank I have in my backpack. Or use the power bank as a pass-through to use both the cables. Or accept the fate and shutdown my primary phone partially* or completely.
*Partial shutdown means disabling certain services and features to save power without fully shutting down everything. This does usually not mean using a battery saver. I use MIUI, it is already fairly unpredictable and regular battery saver** only makes this situation worse.
**There’s also ultra battery saver which kills everything deemed unnecessary running in the background. That couldn’t be more predictable.
That also turns off some other stuff for whatever reason (Bluetooth, WiFi client, WiFi hotspot, Legacy WiFi direct group). I only use the hidden “Disable mobile radio power” toggle. A bit more control that way.
Disabling Bluetooth for example has the undesired effect of disabling Bluetooth Tethering which then needs to be manually re-enabled, and it’s not like Bluetooth creates noticeable battery drain. That’s kinda its point. Low energy requirements.
