For use this Hercule filetype and snippet, follow this 3 steps.

First:
Modify filetypes_extensions.conf. On Linux systems,
this file is located at ~/.config/geany/filetypes_extensions.conf.
If the file does not exist, copy the file
filetypes_extensions.conf in your folder and skip this step.

Once the file has been opened, add the below code to the file.

(NOTE: “…” represents existing data in the file.)
---------------------------------
| [Extensions]                  |
| ...                           |
| Hercule=*.txt;                |
| ...                           |
|                               |
| [Groups]                      |
| ...                           |
| Misc=...;Hercule;             |
| ...                           |
---------------------------------

Second:
Then add the file filetypes.Hercule.conf into your folder ~/.config/geany/filedefs/

Third:
Open the file snippets.conf and copy the [Hercule] sections
at the end of your snippets file in ~/.config/geany/snippets.conf.