For private questions, you can always e-mail the lead developer of Complementary.
emingyildiz@gmail.com
Discord
For casual questions, suggestions and to get support; you can join the Complementary Discord community.
Complementary Server on Discord
Patreon
If you want to support the development of Complementary Shaders and get some little benefits, you can become a patron.
EminGT on Patreon
Github
If you are interested in code, you can take a look and even make pull requests on Github.
Complementary Development on Github