Hi @iwrnd,
The problem is not being too long, it's that you are mixing variable statements. So state the formula that takes care of the day first. Then add a new text element and state the formula for the months as a separate entity. If you want the numerical date as well, that would even be a 3rd additional text element for the #Dd#, or add it to one of the two above
You have the day portion correct except for the end:
$#DOW#=0?Dimanche:$$#DOW#=1?Lundi:$$#DOW#=2?Mardi:$$#DOW#=3?Mercredi:$$#DOW#=4?Jeudi:$$#DOW#=5?Vendredi:$$#DOW#=6?Samedi:$
This is a standard nested IF statement you might see in other computer programming languages. It would look (roughly) like this in Visual Basic:
If day-of-week = 0 Then
say Dimanche
Elseif day-of-week = 1 Then
say Lundi
Elseif day-of-week = 2 Then
say Mardi
Elseif day-of-week = 3 Then
say Mercredi
Elseif day-of-week = 4 Then
say Jeudi
Elseif day-of-week = 5 Then
say Vendredi
Elseif day-of-week = 6 Then
say Samedi
Otherwise
say nothing
End If
So use the same format for the French months:
$#DM #=1?Janvier:$$#DM#=2?Février:$$#DM#=3?Mars:$$#DM#=4?Avril:$$#DM#=5?Mai:$$#DM#=6?Juin:$$#DM#=7? Juillet:$$#DM#=8?Août:$$#DM#=9?Septembre:$$#DM#=10?Octobre:$$#DM#=11?Novembre:$$#DM#=12?Décembre:$
All on one line:
You can't have two conditional statements $...$ $...$ in one element, but you can combine the date with the day conditional by just adding it to the end:
$#DM #=1?Janvier:$$#DM#=2?Février:$$#DM#=3?Mars:$$#DM#=4?Avril:$$#DM#=5?Mai:$$#DM#=6?Juin:$$#DM#=7? Juillet:$$#DM#=8?Août:$$#DM#=9?Septembre:$$#DM#=10?Octobre:$$#DM#=11?Novembre:$$#DM#=12?Décembre:$ #Dd#
Then add the months as a separate element. You can make them stick together by right-justifying the Day-Date:

Then left-justify the months on the same line:

If you have the room, I think you'll be better off on two lines. The Day-Date on top and the Months underneath. That stack will always be centered as the lengths change.
Samples below - Inspection is on.
HTH, John