By crouching during jump you can reach high areas that are otherwise unavailable. Script eliminates the necessity to hold the crouch key.
"Crouch jump script" commonly used by players (crouch jump by holding spacebar):
bind space +duckjump
alias +duckjump "+jump;+duck"
alias -duckjump "-jump;-duck"
There are drawbacks, the jump length is reduced due to crouching. Can the script be improved to trigger crouch after holding jump key for a certain period of time, for example one second?
What I've Seen
I've had a look around but I can't seem to find anything within csgo that could produce what you want
The csgo scripting language doesn't include a way to delay commands by a certain amount of time
I even explored the possibility of adding some python code that could produce what you want. It may be possible but adding or affecting the game files will most likely get you in trouble with VAC
Summary
From what I have seen there is nothing you will be able to do to produce what you want
You will have to just put up with the drawbacks
