If this is in the WIKI or other documentation I have simply not come across it yet. I started a background while reading the tutorial and other docs as the interface is quite similar to how Constructs works (GameDevelop looks to be a better offering) so I began placing tiled images for grass, water, etc. I only have about 5 parent objects thus far that have several instances each placed on the map.
I had placed some grass, dirt and water with no issues but when I began adding some rock for cliffs things went a little weird. It would take the first tiled image just fine but when I tried to insert the next one the editor deleted the previous rock tiles as well as the lake tiles (which were inserted just prior to the first rock tiles). This was originally all on the same layer but my next though was to move the rock tiles up a layer which I have not actually tried yet.
Is there a limit to total instances of an object that can be placed on a layer?
Thanks. I promise I am reading the documentation and I have been punching keywords everywhere looking for an answer.
No, there is no limit… instances number is only limited by memory (anyway, to have a “smooth” game, you could add a LOT of them 
)
Maybe you are adding objects without changing the Z-Order, the Z-Order is a virtual plane, it determines the order to draw the objects (a bigger value, the object is drawed over others). If you add a lot of overlapping objects with the same Z-Order, GD doesn’t know the order to draw and GD will draw some objects first, then some others randomly.
To change the Z-Order: In scene editor ==> press Right click over the object ==> Properties ==> Z Order
…In events editor ==> Acions ==> All objects ==> Z order
Thanks so much. I started adding the rock one layer up and it is working fine but I am going to go back and edit the Z order, that makes more sense to me.
One more question about objects. When making groups in the object’s editor is it possible to only have the object listed within the group. For example: I have ten instances of an object all sitting in the list with other objects. Can these be consolidated so that they only appear in the group list when expanded?