I have multiple wav files with multiple channel audio already in them.
I want to merge them but am finding it difficult to find a way to do so.
I don’t want to change channels or anything just append #1 before #2 and #3 after #2 and #4 after #3 that already have their original L R C LFE Lb Rb Ls Rs channels in them.
Audacity seems to only want 4GB or lower projects as well so it seems Audacity is not the correct software to be using?
I don’t know about the other issues but the 4GB limit applies on any WAV file. It is a limitation of that format and not due to Audacity. You will face that problem whatever you use.
Mark B
That’s strange because I can make much bigger wav files with eac3to from thd.
You don’t have to take my word for it, just look up the file specs. The information is out there.
Well, why can I make a wav file bigger than 4 gigs but you’re staying 4 gigs is the limit is my question. Is there a certain type of wav that can be over 4 gigs?
This wikipedia article might help: All about WAV files.
In the export window, Audio Options → Custom Mapping → Configure will allow you to select the number of output channels and “map” the tracks to output channels.
About the WAV limits -
As far as I know, WAV is the only format with an “artificial” limit.
In the file header there is a 32-bit file size field. With 32-bits you can only “count to” 4GB. (1)
Sometimes you can make a bigger file but usually the file size “rolls over” and starts again at zero.
Some player software will only play the 1st part of the file (which will be a very short section if it’s only a little over 4GB) and other software will ignore it and play the whole file.
So, use another format. 
FLAC is lossless and the file will be almost half the size. Or there is a WAV variation called W64 format that you should be able to create if you have FFmpeg installed. Or maybe F64.
BWF should be OK but I don’t see that option with FFmpeg in Audacity so you might have to export as FLAC and then convert with another tool.
(1) The actual limit when converted from binary to decimal is 4,294,967,295.
Ok that makes sense.