Glad it’s working for you! And your question is easily doable. I'm no longer at my computer to supply you with a full script but adjust the set its position line as follows:
set its position to {(mouseX - 10), (mouseY - 10)}
Basically that subtracts 10 right and below the mouse position. Adjust those numbers until the GMP appears with the mouse over the first selection.
Edit: since I’m on my phone that script might not be formatted correctly but you get the idea 
Edit 2: I'm back at a computer... the numbers need to be larger, at least on my MacBook. Try this:
----------------------------------------------------------
# Author: Chris Thomerson
#
# Current Version: 1.0
# Version History: 1.0 (Initial script)
#
# Created: Wednesday, December 29, 2021
# Modified: Wednesday, December 29, 2021
# macOS: 11.6.2 (Big Sur)
#
# DISCLAIMER
# Permission to use, copy, modify, and/or distribute this
# software for any purpose with or without fee is hereby granted.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
# WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
# WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
# THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR
# CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
# LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
# NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
# CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
----------------------------------------------------------
### Requires Keyboard Maestro 8.0.3+ ###
set kmInst to system attribute "KMINSTANCE"
tell application "Keyboard Maestro Engine"
set mouseX to getvariable "local_mouseX" instance kmInst
set mouseY to getvariable "local_mouseY" instance kmInst
end tell
tell application "System Events"
tell application process "Keyboard Maestro Engine"
repeat until window "Keyboard Maestro" exists
delay 1.001
end repeat
tell window "Keyboard Maestro"
set its position to {(mouseX - 50), (mouseY - 40)}
end tell
end tell
end tell