Presumption: You are using GA4 + GTM (optional) You submit to GA a custom event (e.g. mycustomevent) with some event parameters e.g. {"key1": "value1", "key2": "value2"} Now you want to generate a report based on `key1` to see how many events happened Here is how: You first define a "Custom Definition" As of this writing, it is in: Admin - Property Settings - Data display - Custom definitions Click "Create Custom Dimension" Set whatever dimension name you want. For example in my case the name is: "Key 1" Scope set to "event" (default) Enter any description, or not if you don't want to Event parameter: enter value that is "Exactly" as you defined in event parameters. For example in my case, it is "key1" Click save. Now go to "Explorer" in your GA dashboard on the left Create or select a report you want to edit In "dimension" on the left, click the "+" b...