It would be nice to have the option to lock notes so that they are not accidentally deleted or overwritten (with an error message saying something like, “This note is locked. Would you like to unlock this note in order to delete, edit, etc?”
A further feature to this would be to have locked notes not show the edit section (desktop app). Locked notes can be denoted with a special icon.
The best solution probably would have to have a recycle bin where the deleted notes will go, that way even if it’s accidentally deleted it can be recovered.
That’s also another option which would work well. I think that if you do a recycle bin, you should also consider:
In terms of being able to restore messages, there should be some thought given to the destination notebook of the note. Ideally, it should restore the same notebook it was deleted from, but what happens if you try to restore a note where the notebook was removed? Should there be an option to attached to a new notebook? Something like, “The original notebook that this belonged to, “Fitness Notes” doesn’t exist anymore. Please select a new notebook to restore to:”
Most likely what will be implemented is whatever is the easiest. It’s always tricky to have to track everywhere what’s deleted or not in an application, so maybe it will be a regular notebook where notes are moved when they are deleted. Then it’s up to the user to move them back to “undelete” as they wish. That notebook won’t be synced and indeed we could have something like permanent auto-delete after a few days.
Maybe there could be an entry in the notes’ metadata, saying which notebook it was from? The ‘restore’ could then move it back there (and remove the info from metadata).
Also not sure about the “regular notebook” bit - one would preferably want special handling, like having the notes for read-only access. (It would only lead to confusion - I’m editing a file in this notebook, then suddenly after 30 days my note is gone. 
)
Also, why not have it synced? If I’ve effed something up on mobile, and realize it while on the desktop, I would really like the option to restore it from there.
And while I’d like a “delete everything older than 30 days” function, I would never want it to run automatically. (Sometimes I’m sorting my notes “when I have time”, which may take a looong while, and I like to know they stay in the trash bin until I’m sure the process is done and I no longer need them.)
I thought about this before and it would be strange to have deleted notes being synced everywhere. Like you delete a notebook of 20 notes and then you see 20 items being synced on all your devices. Would users want this? I’m actually wondering? I think in Evernote if you delete, it stays on the device, or do they sync them too?
That will definitely be optional. There will be a deletion date so it will be possible to see which ones are the oldest and manually delete them as needed. We could indeed also store with this metadata the original notebook ID.
Yes that makes sense, the notebook notes should be read-only.
How about keeping the deleted notes in .bin folder like you’ve done for .resources folder? The notes will be there in host service (Dropbox etc.) for 30days for people to undo what they did.
The problem is that going to the sync target to undelete something would not be very intuitive. It would still be better than now (since the notes are permanently deleted), but hopefully we can find a more user friendly way.
How about Bin section with a list of notes in .bin folder?
[Del note 1](:/6g42edcc02f04f2583fac21a656gh537)
[Del note 2](:/...)
Right click restore. Notes will be listed but not automatically download unless specifically requested.
Of course, easier said than done.
Thanks for your hard work @laurent.
I did a fresh install of EN in a VM. Trash seems to be synced, just as expected.
Re all the rest: Great! 
Personally I would like to lock notes for my own security. My brain is ‘busy’, and sometimes I walk away from my computer or phone when they’re open. I keep lots of normal info in Onenote, but also lots of stuff I keep secure in a locked Onenote file. It would be fantastic to know those particular banking details etc were all carefully locked away behind an extra password in Joplin! Anyway, I love what I’m seeing here — keep up the great work!