To be specific - When attempting to perform and/or record a legato action only a single voice is available.
There’s the choice of mono or polyphonic instruments however; when mono - let there be an option for legato/portamento.
afta8’s awesome doofer solves this however it would be convenient if it was ‘built-in’ to the sampler as with most samplers 
although i would hope the glide pattern effect will remain.