Question: ( )( ): Is the use of two pairs of parenthesis in commands explained somewhere?

Occasionally commands in the form of (exprseq1)(exprseq1) are proposed.

(as the solution in https://www.mapleprimes.com/questions/232263-Subscripts-In-Maple)

Questions:

• Is this syntax and its use documented somewhere?
• Can the first parenthesis (exprseq1) be considered as an operator?
• In which situations such commands are preferable?

I had look at Maples help system but could not find any further explanations. What I found so far:
syntax talks about parenthesized expression and refers to
operators,precedence which does not define the precedence of parenthesis
examples,functional two examples show the use of functional operators within rounded brackets
help("Definition,bracket") explains the different types of brackets [moderator note: in common mathematical parlance, not in the technical sense in Maple].

ProgrammingGuide,Chapter02 only refers to a pair of rounded brackets but not 2 pairs
The left and right parentheses group terms in an expression, arguments in a function call, and parameters in a procedure definition.

...

The left and right parentheses are also used to select components from certain data structures (programmer indexing).