Using some techniques from Order items in enumerate
environment automatically, you can reverse the list on the LaTeX side. It will still display in sequential order as you place them within LyX, but will be reversed in the output.
Add the following to your Document > Settings... > Local Layout:
Format 60
Style Reverse_Enumerate
Category List
Margin Static
LatexType Item_Environment
LatexName reverseenum
NextNoIndent 1
ToggleIndent Never
LeftMargin MMN
LabelSep xx
ParSkip 0.0
ItemSep 0.2
TopSep 0.7
BottomSep 0.7
ParSep 0.3
Align Block
AlignPossible Block, Left
LabelType Enumerate
LabelCounter "enum"
HTMLTag ol
HTMLItem li
HTMLLabel NONE
RefPrefix enu
End
The above defines a new environment Reverse Enumerate
that you can choose from your paragraph drop-down:

It is virtually similar to the Enumerate
construction, only with a different name and associated with a different LaTeX environment reverseenum
as well as the removal of the Insert > Custom Item option. Now add the definition of the reverseenum
environment to your Document > Settings... > LaTeX Preamble:
% Using some ideas from
% https://tex.stackexchange.com/q/128297/5764
\usepackage{environ}
\makeatletter
\newcounter{reverseenum}\newcounter{listcount}[reverseenum]%
\let\olditem\item% Store regular \item macro
\NewEnviron{reverseenum}{%
\stepcounter{reverseenum}% New reverseenum environment (also resets listcount)
\g@addto@macro{\BODY}{\item\relax\item}% Used to delimit the items; last item identified by \item\relax\item
\def\item##1\item{% Redefine \item to capture contents
\def\optarg{##1}%
\expandafter\ifx\optarg\relax\else% Last item not reached
\stepcounter{listcount}% Next item being processed
\global\@namedef{reverseenum@\thereverseenum @\thelistcount}{##1}% Store item in control sequence
\expandafter\item% Recursively continue processing items
\fi
}
\BODY% Process environment (save items)
\def\reverselist{% How to reverse list, recursively
\ifnum\value{listcount}>0
\olditem \csname reverseenum@\thereverseenum @\thelistcount\endcsname
\addtocounter{listcount}{-1}%
\reverselist
\fi
}
\enumerate\reverselist\endenumerate% Process items
}
\makeatother
The above definition processes the list once, storing each \item
in a specially-named macro. Once the entire environment is processed and the \item
s stored, it re-processes the list by setting the now-stored \item
s in reverse order, stepping backward through the list of specially-named macros.
To that end, consider the following LyX input:

The first list is set under Enumerate
. The second list is set under Reverse Enumerate
. It produces the following PDF output:

It would be trivial to modify the above to work for an Itemize
list as well.
sort
? It can sort things in a number of different ways. There's also asimilar command
for Windows.... – jon Jul 18 '15 at 22:07