There's not a great deal one can do here.
I have attempted to update the various fields to set a new value that is returned by 0x31, but without success.
Maybe the only thing worth noting is that the second argument is 0x02, which is what is returned by 0x31 when a digit is selected (as it is with Pin-Code). Also, that the third argument- 0x20, has the flush bit set. These might be used by the older GT, or MID?
# Open Dial/Home
C8 06 3B 21 42 02 20 B4
# ^ *
# ^ value returned by 0x31
# * flush bit set 0b0010_0000 => 0x20
NOTE: Last Numbers is in a separate doc.
# Press event
Input > Dial > Digit > 0 3B 06 C8 31 42 02 00 <CS>
Input > Dial > Digit > 1 3B 06 C8 31 42 02 01 <CS>
Input > Dial > Digit > 2 3B 06 C8 31 42 02 02 <CS>
Input > Dial > Digit > 3 3B 06 C8 31 42 02 03 <CS>
Input > Dial > Digit > 4 3B 06 C8 31 42 02 04 <CS>
Input > Dial > Digit > 5 3B 06 C8 31 42 02 05 <CS>
Input > Dial > Digit > 6 3B 06 C8 31 42 02 06 <CS>
Input > Dial > Digit > 7 3B 06 C8 31 42 02 07 <CS>
Input > Dial > Digit > 8 3B 06 C8 31 42 02 08 <CS>
Input > Dial > Digit > 9 3B 06 C8 31 42 02 09 <CS>
Input > Dial > Digit > <- 3B 06 C8 31 42 02 0a <CS>
Input > Dial > Digit > * 3B 06 C8 31 42 02 1a <CS>
Input > Dial > Digit > # 3B 06 C8 31 42 02 1b <CS>
Input > Dial > SOS > SOS 3B 06 C8 31 42 05 08 <CS>
Input > Dial > Open > Messaging 3B 06 C8 31 42 07 1d <CS>
Input > Dial > Open > Directory 3B 06 C8 31 42 07 1f <CS>
Input > Dial > Info > Info 3B 06 C8 31 42 08 0a <CS>
# Note: selecting Top 8 sends command 0x20
# Hold and Release add 0x20 and 0x40 respectively to last byte
# Example: Input Dial Digit 7
3B 06 C8 31 42 02 07 <CS> # Press
3B 06 C8 31 42 02 27 <CS> # Hold
3B 06 C8 31 42 02 47 <CS> # Release
# Dial number buffer
# factory telephone has leading character "_", i.e. "123_"
C8 <LEN> 3B 23 63 00 "5551234" <CS>
# Clear number buffer
C8 05 3B 23 61 20 94
# ^
# Factory unit sets IKE argument regardless of sending to GT,
# or broadcast.
The factory usually has a leading character "_"