Hi @Ruudjuhhh - it’s some custom code I did 
I’ve been wanting the feature for some time and hoped it would be incoroporated.
Anyway, check out my original thread…
How about a selectable Elevation angle column in SkyAware?
…and more recently…
Add a/c bearing and elevation angle to map table columns?
Knowing elevation angles is any easy way to spot lift conditions such as Tropospheric ducting.
In addition to providing the extra selectable column, on the map I make the aircraft “flash” (actually they alternate between red and their regular height dependent colour) every other second.
This makes it easy to spot zones of the country where ducting is occuring. Sometimes it is fascinating to watch.
Due to waning high pressure, conditions are up again earlier this morning (28/03/2022) as I am seeing a couple of ground stations that are normally below my horizon:
Good luck if you make the code changes (several files need an edit in my implementation), but make sure you back up any originals first!