create a new step/sequence - cue

I've read the manual up and down, but can't find the answer...
I'm using a showfile of sb and would like to insert a step.
let's say i have
step 1 cue 0
step 2 cue 20
step 3 cue 30
now i'd like to insert a cue between before step 3, which is called cue 25.
what happens when i insert a step, i get a new step
so i have
step 1 cue 0
step 2 cue 20
step 3 cue 0 !!!!!
step 4 cue 30
and cue 0 has of course the same parameters as cue 0.

so HOW DO I INSERT A STEP WITH 1) my own created values of channels, 2) with the number i'd like to call it (may it be 21 or 22 or 29)???

thank you!!!

let's say 'R' the shortcut to record a cue:
25 R

++