I tried now the solution provided by @Euler-37. I think it works perfectly.
One thing that is probably good to mention: there is an editor option conceallevel that seems to have a default value 0. I needed to set it 1 for the conceal feature to have an effect.
Here is an example rendering with my options (on left is the default rendering, on the right is the concealed rendering):
One can also conceal with the more conventional symbol .:
Or some emoji 
:
Notice how the cursor line remains unconcealed. This is due to the concealcursor option that allows to concealment of the matches at cursor line. However, I was not able to alter the default behavior. If Anyone has an idea, let me know.