V1.9.1 Where is the manual K factor management panel ?!

Seems like it depends on your printer firmware, see 2. feature on the beta firmware feature set, which is not released yet: Beta testers for P1 series firmware! - #21 by JonRaymond

Version OTA 01.05.04.00:
[New features)

  1. Non-LAN binding via PIN code on the studio side (in conjunction with Bambu Studio v01.09 Beta4 and up).Users can bind P1 devices to the computer that is not on the same local area network (LAN) using a PIN code on the studio side
  2. Improved manual flow calibration parameters management. (in conjunction with Bambu Studio v01.09 Beta3 and up) Auto-save the manual flow calibration parameters; Support creating managing new PA parameters; Support setting PA configuration files on the filament settings page
  3. Third-party filament support.Users can create and manage custom filament profiles in Studio. These custom filaments can then be selected in Device filament slots
  4. Device name display.Custom device names from Handy or Studio can be displayed in the settings menu
  5. Added carbon rods lead screws maintenance notice
  6. Improved color display for gradient and dual-color filaments
  7. Auto filament verification when printing with 3M files from an SD card