Hello,
we have already Blackpill F411CE in MbedCE but it is not possible to use it with KeilStudio
- MCU Info Page: STM32F411xE · mbed-ce/mbed-os Wiki (github.com)
- STM32 Deploy&Debug · mbed-ce/mbed-os Wiki (github.com)
With classic Mbed you can look here - Bluepill board support for Mbed OS 6 - Custom and community boards - Arm Mbed OS support forum
For Drag&Drop you have to connect VDD_target pin of ST-link to VDD of your MCU (3v3 on SWD header of Blackpill or Bluepill).
BR, Jan