Android Q is a beta (and the FIRST beta), the page you didn't read before installing it says that some features are not available, this would be a feature not available apparently.
Here, I'll help with some of the information you skipped -
Certain functionality (including core functionality, such as your ability to place and receive calls) or applications may not work properly. You are solely responsible for any error, defect, damage or destruction due to such use, including damage to any device or loss of data.
It's very possible that widgets were not a top priority for developer preview 1 (the version that's installed) and will come with a later preview.
Beta versions of software are not intended for regular users to get the new version before others, they're intended for developers to get access to the new version to be sure their apps work properly with it before it comes out.