This process is controlled via GitHub actions.
Once changes have landed on master and manual verification has been completed, go to Releases -> Create a new release.
Tag the version, e.g. "1.9.0" (must be semVer, no letters).
A special action "Deploy to WordPress.org" starts automatically. It deploys the plugin to wp.org and creates an asset (zip file), adding it to the release.
This relies on repo secrets SVN_USERNAME and SVN_PASSWORD; if wp.org credentials are updated, the repo secrets must be updated as well.
The easiest way is to create translations online. Such translations are loaded automatically by the plugin via WordPress Core and require no further amendments to the plugin code.