Spoiler/Speed brake controls

How can I control:

  1. Manual speedbrake: extend/retract manually: I do that in P3D v4.5 and FS X Steam by “/” key.
  2. Auto speedbrake: Arm/disarm speedbrake: I do that In P3D v4.5 and FS X Steam by “Shift+/” key.
    the above in MSFS2020?

Unless I’m missing your question… Just map that key to the action in MSFS. You’ll see a bunch of different spoiler actions in Flight Control Surfaces > Secondary Control Surfaces.