Any active macro can be triggered using the kmtrigger: scheme with a URL like this:

kmtrigger://macro=<MacroNameOrUUID>[&value=<TriggerValue>]

where

"<MacroNameOrUUID>" is either the URL encoded Macro Name, or the Macro UUID
"[&value=<TriggerValue>]" is the option to pass "<TriggerValue>" as the Macro %TriggerValue%
   • Do not include the square brackets [ ] in the actual URL.
   • Do not include the "%value=" without a value.
 

You can pass a trigger value to the macro by adding the “value” query parameter to the URL. The parameter is available to the macro as the %TriggerValue% text token (v7.0+).

For other ways to use a URL to trigger a macro, see:
Macro Triggers that Use a URL, 2018-07-15, peternlewis

kmtrigger://macro=Prompt%20With%20List%20%40TEST
kmtrigger://macro=984A3DBF-5B70-4031-979F-5AD44E3B24A5
kmtrigger://macro=Prompt%20With%20List%20%40TEST&value=MyTriggerValue
kmtrigger://macro=984A3DBF-5B70-4031-979F-5AD44E3B24A5&value=MyTriggerValue

Note that a macro must be active (that is, it must be enabled, and the macro group that contains it must be enabled and active) in order for the macro to be triggered by any means including via URL.

You can get the kmtrigger for a macro by clicking on the “or by URL:” popup in the Trigger section of the macro.

• Execute a Macro
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• %TriggerValue%
• See all Tokens

• Script trigger
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• keyboardmaestro CLI Tool
• Trigger File
• All Triggers

• What exactly are those "keyboardmaestro URL Scheme" actions and how do I use them?
• Keyboard Maestro Forum topics about kmtrigger: scheme