Possible reasons you may want to create your own templates:
You use a standard splash page for your games. Save a template with that splash page already added, open the template for a new project and, voila! You can move on to developing your game.
You have a favorite animation, or sprite, or sprite font, etc... that you often use in your games. Add it/them to your custom template and, boom! It's/they're already there. Ready to go.
You've got a favorite event sheet(s) with loops, arrays, global variables, etc... that you commonly use in your games. Save them in a custom template and, well, you've got the idea by now. They're available for you in an instant, already setup to suit your needs.
In providing these instructions, I am assuming that you are comfortable working with xml files. If not, you might want to avoid doing this.
It's pretty quick. You will have your custom template ready to go in only 7 steps:
1. Create the .capx file that you wish to save as a template.
2. Save it to Program Files/Construct 2/Templates (or wherever your Templates folder exists) and save the .capx file
3. Find and open the folder containing the Construct 2 program files and save a copy of startdlg.xml
4. Open startdlg.xml using Notepad++ (or whatever your favorite code editing software is) *Note: You may need to Run As Administrator when opening your editing software since Windows may not let you save a file in the Program Files folder otherwise.
5. Following the format you see in this file, copy then paste one template block (or type it in manually if you don't want to be lazy like me) and replace the bold text with your own:
<name>Whatever you want to call your template</name>
<description>A description of your template</description>
Example: copy this block of text (highlighted in grey)
... then paste it here (highlighted in grey) and insert your text
6. Save the file
7. Close/Re-open Construct 2, click New Project and open your custom template.
If it doesn't work right, restore your backed-up copy of startdlg.xml.
Thus ends my very first tutorial contribution. I hope this comes in handy for those of you who like using custom templates when you develop.
P.S. Notepad++, which is a great little editor (and it's FREE) may be found here: notepad-plus-plus.org