Running an already recorded route

You can do it at least on Garmin Connect Web (didn't quickly find a way in Garmin Connect Mobile). Just open the activity and use the gear icon on top right.

2654374 said:

Can I rerun exactly the same route again by using it as a navigation?

You did not tell what watch model you own, but on some models you can indeed navigate a past activity. For example on my Instinct I go to the settings of the Run activity (long press the Menu button), and then scroll to Navigation » Activities and select the activity I want to run again.

Otherwise, follow the advice of Bitti and save the activity as Course in Garmin Connect.

Open the activity in Connect on the web.  (connect.garmin.com).  In the upper right corner of the activity there's a gear icon.  Click the icon, then select Save as Course.  Assign it to whatever activity type you're doing and give it a good name.

Now, in Connect on your smart phone, under Training you'll see Courses.  Select the Course you just created on the web app.  Click the three dots on the upper right had side of the screen and select Send to Device.  Pick your watch, and the course will be transferred to your watch.  (You could try to transfer it to your scale, but I don't know what the result would be.  Perhaps the scale will leave the bathroom and run the course?)

Now, the next time your run, after selecting the run app (or whatever), and before you click the start button, click the up button.  Select Courses from the options.  Then select the course you just save to the watch.  Then select Do the Course (or whatever the actual menu name is).  Then when you run, you'll get instructions, etc., on your watch.  Heck, I even get a map.

Note that this works for me, but I've got a 945.  I'm not sure exactly what happens if you're using another watch.