This script lets you to locate your startup apps into ~/.config/autostart/ directory. Just place the .desktop files here and run the script.
To run script run this command:
curl -fsSl https://raw.githubusercontent.com/Elagoht/i3-startup-apps/main/refresh-autostart.py | python
A config file will be created on your i3 config directory. Then you must include that file on your i3 config file.
Simply add this line to your config file:
include ~/.config/i3/startup-apps