Since I updated to gedit 2.29.9, shortcut keys don't work for Snippets, but still work for External Tools. To reproduce the bug:

1) Make sure Snippets are enabled in "Edit > Preferences > Plugins", and go to manage them in "Edit > Preferences > Plugins > Snippets > Configure Plugin".

2) Create a global snippet, named for example "comment":

/* $1 */$0

and create a shortcut key:

Control+n

The "Shortcut key" field is filled with "Ctrl+N". Note: in External Tools, the shortcut key is saved as "<Control>n" (more details below).

3) In gedit, create a new file and do the shortcut key.

Actual result: nothing.

Expected result: the snippet "comment" should be expanded.

Here's a comparison with the plugin External Tools:

1) Make sure External Tools are enabled in "Edit > Preferences > Plugins", and go to manage them in "Edit > Preferences > Plugins > External Tools > Configure Plugin".

2) Create a tool, named for example "copy-name":

#!/bin/sh
echo -n "$GEDIT_CURRENT_DOCUMENT_NAME" | xsel -b -i

and create a shortcut key:

Control+n

The "Shortcut key" field is filled with "<Control>n".

3) In gedit, open a file and do the shortcut key.

Actual result: the tool is run.