wrote...
....
local to the worksheet named ' '

I take this to mean there is a worksheet named by the space-bar
solely, name equal to CHAR(32). Since I don't understand why one
would do that, . . .

It's intended to be a hidden worksheet containing worksheet-level
named formulas and global named ranges. Formulas in other worksheets
would refer to the named ranges but not ranges in the worksheet. Using
' ' (without the single quotes) uses up a potential worksheet name
that is unlikely to be used otherwise, which means it doesn't tie up a
worksheet name I might want to use.

There's nothing necessary about this. If you want to, you could name
the worksheet _ or Utility or ThisShouldBeVeryHidden.

. . . When I try other constructions such as '' (single
quote-single quote), Excel says they are invalid names.
....

Single quotes aren't part of the worksheet's name. They delimit
worksheet names that include spaces. Two single quotes in sequence
would be equivalent to a worksheet name that has no characters at all,
the same as the result of the formula =LEFT("Whatever",0). That's not
a valid worksheet name. Worksheet names need to have *ONE* or more
valid characters.

global
WSLST:
=' '!$1:$1

Isn't this local? And I take it refer to Row 1 of sheet space-bar.

No! This is GLOBAL. Its exists so that formulas in OTHER worksheets
may refer to this named range. Wouldn't that intended use be simpler
if the name were global scope?

_WBWS and WSNAME I understand, though not why the $1:$65536 range.

$1:$65536 remains unaffected no matter which or how many rows, columns
or cells you insert or delete. Since CELL only uses the top-left cell
of its optional second (range reference) argument, this doesn't do any
more work than CELL("Filename",!$A$1).

=INDEX(WSLST,MATCH(WSNAME,WSLST,0)+1)

Returns #N/A for me. It looks to be indexing a list of sheet
names, but I don't see how it was populated. See above.
....

I missed a step in my original posting. Once WSLST is defined, select
it (it's a range, ' '!1:1) and enter the array formula

=_WSLST