Alright, I made good progress on the topic this morning 
I have a first design proposal to present to you: MQTT Virtual devices view
I detail it here in a few screenshots:
Step 1: Device list
More compact list, shown as a list and without repeating what is already in the edit view.
- Grouped by room for better readability and to avoid repeating information
- Easier to scroll on mobile. Easier to visualize all your devices.
- Added a button to reverse the sort order (who wanted reverse alphabetical order?)
- More powerful search bar
Step 2: Device edit view
- More compact view; features are collapsed by default.
- Ability to see at a glance whether a device is being logged
Step 3: Adding a new feature
I was largely inspired by @guim31’s proposal
- Grouped view by categories for easier searching
- Concept explained by a short description
- Display of the feature’s rendering so the user can visualize it
Step 4: Editing a feature
- More compact view.
- In some cases, « unnecessary » fields should be hidden or filled by default (Min/max for example can be filled with sensible values)
Conclusion
This is a first draft; I’m open to feedback
The goal is then to iterate, and once we all agree, we’ll need to do the mobile design, then the list of all device types (for step 3), and write all the copy.
Finally, we can move on to development, but it’s only frontend, nothing too complicated; the hardest part is really agreeing and creating all the content.