You would do better putting your .wav/AIFF files in a handheld playback device. Usually you can make a playlist in such a device.
There is no facility in the Motif XF to create a playlist from your .wav/AIFF files as there would be in the S90XS/S70XS... In which you can create a Seq Chain, a chain can recall a Multi, then play a .wav, recall a Multi, then play another .wav... But even there a chain can only have 100 steps.

A .wav/AIFF can be "auditioned" on the Motif XF, but if you want to play along with its audio, you'd be better off converting the .wav to a Motif XF Waveform. As a Waveform in the XF you have much more control over playing back the Audio. But what an inefficient use of your technology.

But because you mention you have more than 100 such files, we strongly recommend getting a handheld device that is designed to easily playback such files and easily manipulate them. You gain nothing really by transferring more than 100 audio files to your keyboard to play along with... I suggest a handheld device that allows such reorganizing, and can just stream playback. You can connect it stereo out to your Motif XF's A/D Input. Then you have can have control of your instrument as you require.

A device like a Yamaha Pocketrak, or an iPod/iPad, or even your smart phone would be better at organizing these files for playback. If you are using the XF to create the music in these .wav/AIFF files you could use the Yamaha Audio Recorder for Motif XF (iPad app) to upload them to SoundCloud - there you can create playlists and manage all your Wav/AIFF files easily.

This way you're not handicapping your instrument playing back your +100 .wav/AIFF files.