Unfortunately, adding custom dimensions and metrics in Google Analytics 4 (GA4) is murkier compared to Universal Analytics. GA4’s interface only allows selections from existing primary dimensions and metrics for summary card setup, meaning custom ones aren’t readily accessible.
However, it’s possible to create custom dimensions and metrics in GA4 using “Events and parameters”. You’d need to work with a developer or have some coding knowledge to set these up and ensure the values are sent to GA4. Once these are setup, they can then be used in analysis and reporting.
Bear in mind that GA4 is fundamentally different from Universal Analytics, being event-based rather than session-based. This could affect the way you setup and interpret your custom dimensions or metrics. It’s a matter of translating what you want to achieve from Universal Analytics’ perspective to GA4’s setup.
Still, if you’re very comfortable or reliant on using custom dimensions and metrics from Universal Analytics, you might find GA4 a bit limiting for now. You can still use them side by side until you’re fully ready to transition or until GA4 fulfills your needs.