Under construction.
After the limit of the Extended Collapsing-E notation, I propose the extension of the notation and to reach the countable limit of the extended Buchholz's function (better known as the Extended Buchholz's Ordinal in Japanese googology) in all three hierarchies (the fast-growing hierarchy, the Hardy hierarchy, and the slow-growing hierarchy), by allowing delimiters to nest inside subscripts (for instance, the smallest case is &_#, which diagonalizes over the fundamental sequence: {&, &_2, &_3, &_4, &_5, ...}; and the limit of the notation diagonalizes over the fundamental sequence: {&, &_&, &_&_&, &_&_&_&, ...}).