Sublime Text 3 on Ubuntu: custom keybinds in packages - sublimetext3

Question

Problem
My problem is that the custom keybindings that I assign in Sublime Text 3 on Ubuntu are not registered. In my case, I am trying to set them for commands in the 'MarkdownPreview' package.
Setup
I have the following setup:
Ubuntu 16.04
Sublime Text 3 (build 3126)
MarkdownPreview package
Details
My MarkdownPreview.sublime-settings looks as follows (User settings):
[
{"keys": ["alt+m"], "command": "markdown_preview", "args": {"target": "browser", "parser":"markdown"}},
{"enable_mathjax": true}
]
I have already opened the console and set sublime.log_input(True) and sublime.log_commands(True).
The output in the console when pressing alt+m does show the event being registered, but no command is trigged. See this console excerpt:
key evt: backspace
command: left_delete
key evt: alt+m
key evt: control+c
command: copy
I can run the command from the command palette and the "enable_mathjax": true setting works fine

Answer 1

The reason this doesn't work for you is that you've put the key binding in the preferences for the package instead of in the key binding file, where Sublime can't see it.
The mathjax setting you have should be in your MarkdownPrevious.sublime-settings file, as that's a setting for the package. So that file should look like this:
{
/*
Enable or not mathjax support.
*/
"enable_mathjax": true
}
With that done, you want to select Preferences > Key Bindings (or if you're using an older version of sublime, Preferences > Key Bindings - User) and put your key binding in that file:
[
{
"keys": ["alt+m"], "command": "markdown_preview",
"args": {
"target": "browser",
"parser":"markdown"
}
},
]
This shows the complete contents of the key bindings file with only this single key binding. If you have any other custom key bindings, add this to your file without the [ and ] surrounding it (as they will already be in the file).