Can any type of enamel by chance be a clear one by just adding a thinner? For example, a red with amounts of thinner can be clear red. Is is possible?

Not really. All you will be doing is spraying opaque pigments very thinly. Let's look at 2 concrete examples.

White base coat, overspray clear red, get a clear red effect.

White base coat, overspray thin enamel red, get a pink coloration. You will try to spray more to get a deeper red eventually getting the opaque red you were trying to avoid.

Clear Red would cover the White entirely where the thinned solution would allow the white to be seen. Your eyes would translate this into pink.

Hi shonen red

You could try adding the red to gloss varnish to tint it. :-)

All the best

Rowan

Wow! A nice trick! But how much red should I put to make it clear?

The only one way is trying to do it Shonen Red. Tru to mix a few drops of clear varnish with a cocktail stick dipped in red paint (not too wet) and have a look if it works ok otherwise add more color or clean varnish...
Ciao