Pressing "F1" shows "No documentation available" in Help panel

When editing source code the "F1" context help only works for methods with parameters, if the parameters are already filled in the call:

E.g.

QString string; 
string.append({cursor_blinks_here}); // there are 7 overloads !!

If I use CTRL+Space after typing "appe" it will be expanded to "append" and have the cursor in the braces. The tooltip is showing: 1 of 7 ....... possible parameters.
Now I want to press "F1" to get an idea, what the parameters mean.
But I get: "No documentation available"

Ok, move the cursor into "append" and "F1" results in "No documentation available", too.

If I choose a paramter constellation, e.g.

QString string;
string.append("foo"{cursor_blinks_here}); // there are 7 overloads !! 

If I press "F1" ... "no documentation ..."

Now, if I press "F1" while the cursor was moved to be inside "append" I get the help for this exact parameter set I used. Finally
Ok, but a little late.... I already have chosen a version of the 7 and guessed the meaning. No I can check with "F1" if my guessing was right...

I would like to decide which parameter constellation to choose just before I guess.

Wasn't it like this before (in older QtCreators)?