Be able to copy and paste layers on different slides.
Instead of having to create different new layers on every slide of the same layers, the ability to copy those layers and paste them over would save a lot of time. Universal layers that also change size over all slides as you change the size of them on one slide would also be extremely helpful.
You can do this by linking your layers. Then in each scene, when you click Add Layer, you can add this linked alert layer and its settings will be preserved from the other scene in which it was created. A linked layer allows you to seamlessly make edits to any layer across all scenes from one scene. Linked layers share all properties except their position, so you can adjust the layer's placement to best suit the current scene you're editing without affecting its placement in other scenes; however you won't need to edit every other aspect of it. Hope that helps.
Having layer groups would be so useful and as far as I know isnt available in OBS (looks like it is in xSplit). Your layers can get cluttered really quickly and having groups or folders would make cleaning it up really easy!
Simply copy/pasting the same layers (specifically things like repeated browser sources for alerts, etc) seems to put a lot of strain on the CPU. It would be nice to have a setting under each layer that allows it to mirror an existing layer from a different scene without creating a whole new instance.
The ability to select multiple layers at the same time, group them, copy and paste them into another layout. Just like photoshop.
that way one layout can be used as a layer in a bunch of different layouts