I have seen somewhere, that to join the string inside block,
this is used:

 

Code

something = "Today close price is: " + variable;

but i cant make it work with:

 

Code

plot1(high, "Plotnamee:"+variable);

how to merge the two strings to make it Plot name?

I'd try something like the following (can't test it myself now):

 

Code

plot1(high, Text("Plotnamee:"+variable));

It can also be that using dynamic names for the plot name isn't allowed.