Hi, I would like to give an example setup to explain me problem. Lets say I have a blueprint with two instanced static mesh components and I place a copy of this bp in the world. The first ismc is holding a dorrframe mesh, the second is holding a doorframe molding mesh. I can alt drag the doorframes around the world to automatically create instances in the component array, but to save myself a lot of time, I have an editor exposed function in the bp that loops through all the doorframe instances and places two moldings on either side of the doorframe. This will work fine if there is no rotation on the doorframe, but once there is, if I just use the doorframe’s transforms solely to determine the molding’s transforms, then the location is not based on the local transform of the doorframe.
If needed, I can provide some screenshots for more reference, but basically, I’m just looking for a way to at least simulate the molding instances to act like they are grouped under the doorframe instances.
Please also keep in mind this is just an example, and I have some more complex ideas I’d like to also make, which further requires some kind of way to group instances, not just grouping the components themselves, if this is possible, thanks.
why does it need to “act like they are grouped under the doorframe” when you can actually just group them through SetupAttachment() (C++) or AttachComponent()(blueprints) then set the relative rotation of the thing being added so that it corresponds to the rotation of in this case the “DoorFrame”
if thingX shall always have thingY, then why not just group them together to begin with?
When you alt drag the blueprint, a new pair of instanced static meshes are created.
If you really want to have 2 ISMs, you have to do it in one blueprint.
Also, the whole point of making blueprints, is you can put them all over the world, and they work, no matter what angle they’re at ( if written correctly ).
If you REALLY want to do this with only two ISMs, then you need a second BP to handle instance management, and the door BP will have to ask to have it’s meshes made.
Bit of a nightmare 
I’ve got a plugin (rdInst) on the marketplace that manages ISMs/HISMs in a singleton - it takes care of the instances for you - you just add/move/remove.
Regarding the BPs rotation - you do need to combine the transforms in your routine when using a singleton instance generator as the instances are in worldspace (rdInst takes care of the locations when you subclass your blueprints from it’s “rdActor”)
Thanks for the replies everyone. As scene in the attached image, I am using the two ISMs in one bp, and I was trying to do something with the attach components node, but that node doesn’t look to work with individual instances from the ism component. But if the individual instances only deal with world space, then I may need to look at everyone’s suggestions, and rethink things some more.