Try an "If" action with a "Script" condition:
...where the result is 1
when the timer is running, 0
if not (because there will be 0
menu bar items with the description "Timer"
).
The AppleScript is:
tell application "System Events"
tell application process "Control Centre"
return count of (every menu bar item of menu bar 1 whose description is "Timer")
end tell
end tell