WTH Ability to create user-defined device entity

[petro]

I can close it, but I’ll find the other threads. Many flavors:

WTH can't I manually assign entities to devices

Some context: The Devices system has always been slightly confusing to me. Everything is fine when a device and all its entities are from a single integration. However, sometimes entities from other integrations are attached to a device that already exists. (E.g. a device tracker from my WiFi AP attaches to the Samsung TV device.) Perhaps this uses MAC addresses to match the devices? It is a very nice feature to have, but it doesn’t work 100% of the time. This results in duplicate devices or “…

Why can't we create custom MQTT devices?

Allow the ability to create a custom device which can contain multiple entities. For example defining multiple entities for my smart meter’s MQTT feed results in multiple entities, however it would be great to pull these all together under a single device.

Why can't we add template entities to existing devices?

Template entities are great. However if you need to template a value for a specific device, there’s no way to link it to the original device?

Wth can't I add a helper to a existing device?

I have helpers like input_booleans and input_select that I have made to help control a certain device it would be great if I could just add these entities to the relevant device.