How to check for a specific substring in a .yml file with Skript

[Goose]

Hey guys! I wanted to make a GUI for Group Manager that can list the groups in a GUI, so in order to know all the groups, I need to go into the groups.yml file of Group Manager and when the script finds a group, it would set it a lime terracotta with the name of that group. How would I do this? (Hopefully that made sense :v)

CODE:

# functions (required for script)
function i(t: text, p: player):
make {_p} execute command "/skGroupManager %{_t}%"

command /skGroupManager [<text>] [<text>]:
    description: A plugin written with Skript that uses an easy-to-use GUI for simple set-up! (Requires Group Manager)
    permission: skGM.command
    permission message: You do not have the permission "skGM.command", so you can't use this command.
    aliases: /skGM [<text>] [<text>]
    trigger:
        open virtual chest with 4 rows named "&b&lskGroupManager GUI" to player
        format gui slot 2 of player with lime terracotta named "&a&lCreate a group" to close and run function i{"create group"}
        format gui slot 4 of player with red terracotta named "&c&lDelete a group" to close then run function i{"delete group"}
        format gui slot 6 of player with light blue terracotta named "&b&lList all groups" to close then run function i{"list groups"}