TLDR; flash the zip from recovery

Yep. It's a "nobody asked" kinda feature. But I like messing up with the LK and so I made it. I just utilised an unused logo show function that is responsible for charger high voltage warning and replaced that particular image (img62.png for rui3 and img4.png for rui2) using logo builder v.1.6 to show Fastboot (GUI - like) menu. You can flash the zip (contains LK and logo) directly from recovery and make use of it. If you're using a custom splash already, make sure to replace that splash manually and flash the new logo. I've added the full kit plus some custom splashes [click to download] required for making your own splash logo or even make your own fastboot splash.

If you're using the lock spoof LK, you must flash this (rui3 only for now cuz nobody is using lock spoof rui2 version so far).

Any suggestions/feedback - dm me @antagonizzzt