Gdevelop expressions look overly verbose. Anyways, I’m not sure the question.
The math of positioning an object with a distance and angle from another object is the same no matter the program.
X = centerX + dist*cos(ang)
Y = centerY + dist*sin(ang)
Or since you know the object you want to move toward you can skip the trig altogether.
mag = distance(centerX,centerY,mouse.X,mouse.Y)
X = centerX + dist* (mouse.x-centerX)/mag
Y = centerY + dist* (mouse.y-centerY)/mag
Although you could use the move at angle or move forward actions to do that too in construct.
Sprite: set position to (centerX,centerY)
Sprite: set angle toward position (mouse.x,mouse.y)
Sprite: move forward dist pixels.
There are likely other ways too. My answers are construct centric.