How to modify domain's configurations in Plesk permanently

Question

How to modify domain's configurations in Plesk permanently?

Answer

The recommended way to modify virtual hosts settings is using Plesk interface in Domains > example.com > Apache & nginx settings or in Service Plans menu. However, it is possible to edit the default templates located at /usr/local/psa/admin/conf/templates

See this documentation for more instructions:

Changing Virtual Host Settings Using Configuration Templates

Warning: Do not change the default templates. To introduce your changes to the configuration, copy the required templates to the /usr/local/psa/admin/conf/templates/custom/ directory, preserving the directory structure, and then modify these copies. It is possible to create new templates from scratch and place them in the custom/ directory according to the default structure.