"grouping"... I don't undestand it

hi! I've recently switched from i3 and X11 to Sway and Wayland. I used to run Dunst and switched to Mako, and asked Claude (I know, I know) to re-write the config for me.

One of the parts that is not worked as I inteded: grouping, I've checked #66 and #111 and I can't get my head around.

In dunst, for the same application (mostly for chats like slack or whatsapp) I would get a stack of lines in the same notification widget.

That doesn't seem to be working with mako. I either still get one notification per-message, or only the _last_ message

Here's my mako config (bits that I think matter)
```
default-timeout=5000
ignore-timeout=0
max-visible=5
layer=overlay
group-by=app-name

[grouped]
invisible=0 # I've played with this value

[group-index=0] # I've played with this value
invisible=0 # I've played with this value
```

What I would like to have is something like
```
* App Name
-message 1
-message 2
```

Instead of
```
* App Name
-message 1

* App Name
-message 2
```

Start by reading issues #66 and #111, then reproduce the reported behavior with the provided Mako configuration and grouped notifications from one application. Determine whether grouping is intended to stack message bodies or only replace notifications, and document or fix the behavior so the result matches the requested grouped layout.

Written by the indexing model from the issue text.