Additionnal or existing variable and macro coming from grafana

when writing url for links, sometimes I want to use the username logged, the root url of grafana, dashboard id or title, …
Is there some variable accessible from ${} as the data from the query ?

this kind of variable coulb be used in the query too

I didn t found a list of accessible variable
I checked something in js in a txt panel, but I don t think it s a good way,