@Nokel81 This appears to be a problem with your user configured keybindings.json. By default, we do not ship with cmd+j bound to join lines. I am guessing that the problem is a missing context key, e.g.:

{ "key": "cmd+j", "command": "editor.action.joinLines", "when": "textInputFocus" }

Can you please double check your keybindings?

Sorry for the late response. This is the content of my keybindings.json file:

// Place your key bindings in this file to override the defaults
[
]

This is what I see when I searched for "join" in the keyboard shortcuts UI.

@Nokel81 I think this is a keybinding contributed by one of your extensions. Could you please try the following:

• Run the command Developer: Toggle Keyboard Shortcuts Troubleshooting
  • This will activate logging of dispatched keyboard shortcuts and will open an output panel with the corresponding log file.
• You can then press cmd+j and check what keyboard shortcut VS Code detects and what command is invoked.

This will output if the keybinding rule is a built-in one or contributed by an extension.

If you are having trouble understanding the output, please feel free to paste here and we can help decipher it for you.

This is the relevant logs:

[2020-11-18 13:59:55.901] [renderer1] [info] [KeybindingService]: / Received  keydown event - modifiers: [meta], code: MetaLeft, keyCode: 91, key: Meta
[2020-11-18 13:59:55.901] [renderer1] [info] [KeybindingService]: | Converted keydown event - modifiers: [meta], code: MetaLeft, keyCode: 57 ('Meta')
[2020-11-18 13:59:55.901] [renderer1] [info] [KeybindingService]: \ Keyboard event cannot be dispatched.
[2020-11-18 13:59:56.168] [renderer1] [info] [KeybindingService]: / Received  keydown event - modifiers: [meta], code: KeyJ, keyCode: 74, key: j
[2020-11-18 13:59:56.168] [renderer1] [info] [KeybindingService]: | Converted keydown event - modifiers: [meta], code: KeyJ, keyCode: 40 ('J')
[2020-11-18 13:59:56.168] [renderer1] [info] [KeybindingService]: | Resolving meta+[KeyJ]
[2020-11-18 13:59:56.168] [renderer1] [info] [KeybindingService]: \ From 2 keybinding entries, matched editor.action.joinLines, when: no when condition, source: built-in extension ms-vscode.atom-keybindings.

Namely, this shows that it is the "built-in extension ms-vscode.atom-keybindings"

• Oh, that's a bug in the debugged output. ms-vscode.atom-keybindings is an extension, but not a built-in extension. The output should read: "source: extension ms-vscode.atom-keybindings". I suggest we use this issue to track this bug.
• Basically the atom keybindings extension defines cmd+j for join lines, but forgets to define a when clause. Let's track that at Join Lines (cmd+j) should use a "when" clause. vscode-atom-keybindings#70

Until microsoft/vscode-atom-keybindings#70 is addressed, you can use the following in your keybindings.json:

{ "key":"cmd+j", "command":"-editor.action.joinLines" }, // remove the keybinding with missing when clause
{ "key":"cmd+j", "command":"editor.action.joinLines", "when": "editorTextFocus && !editorReadonly" },

Thanks for the quick response and will do.