Choose or remove detected planes

hey guys...I need your help!
for my bachelor degree I am developing an "Ikea" like app where you can place different objects (some are animated) on different surfaces. so far everything works fine...there's just one thing where I am struggling with! for the plane detection I am using the result type "existing plane"...so I can place the object on the entire plane/surface. but the problem is...when i detect the first surface (floor) and move the mobile device to detect another surface (table)...i have to go below the the second surface (table) to place an object on the first detected surface (floor) because its on a lower level. i know the problem is the result type of "existing plane" because it covers the world on this plane and i could use "existing plane extent" to solve the problem quickly but i wanna use this type. there must be a way to choose a specific plane for the raycast? like dropdown menu or something? because in the sdk are events like "plane added", "plane updated" and "plane removed"! but stupid how i am i don't know how to use them! so would be great if anybody could help me...thx

 

You should be using existingplanewithextent - existingplane means an infinite plane at the level of the plane detected