@javasquez 

I came across the same behaviour with a paused Continuous job that Run now was enabled but Run now with different settings remained disabled in the UI.

I tried triggering the same job through the Databricks SDK with overridden job parameter as:

from databricks.sdk import WorkspaceClient
w = WorkspaceClient()
w.jobs.run_now(
    job_id=<job_id>,
    job_parameters={"mode": "override"}
)

 The run started successfully and the parameter showed as override (resolved) in the job run.

So this looks like a UI limitation for Continuous jobs, while parameter overrides still work through the Jobs API/SDK.