...Is it possible?

I enjoy selecting ever map with the settings on "Play In Random Order" so that I do not know what to expect. However when I press select all followed by add to list I receive a message informing me that the Map List is full and only get about half the maps on the play list.

Is there anyway I can increase the capacity of the play list? Hex editing maybe?

There is a variable that can be changed in the shell to increase the list's max length. I've always assumed it is a game limitation, in that the game can't handle a map list larger then that, so I've never tried changing it and don't plan to.

You can just select your bottom half (or top half) of the maps and include all those.