Usually we use crontab -e command, while logged in as a user, to modify the user’s cron jobs or crontab -e -u[user] as root.
The editor used fot this depends on the system variable VISUAL or EDITOR (if present) else the default editor will be used /usr/bin/editor.
So if the default editor is a not well known program (take “VI” as an example, even if you use the more user friendly “VIM”…), you can modify the suggested system variables if present, to verify:
set | grep -iE ‘(visual)|(editor)’