Bitwig's 2.4 update from a couple of weeks back saw the overhaul of the Sampler instrument. Making it a more comprehensive way to create sample and multi-sample instruments.
With up to 8 sample layers, keygroups and granular possibilities, it offers way more synthesis and sound design possibilities.As with many of the Bitwig devices, many many parameters are modulatable by their included modulators.
Creation and editing of multi-sample instruments has also been overhauled to make it more straightforward with plenty of drag and drop actions to set up the initial instrument and keygroups- as David says "Its not much fun editing multi-samples".
Bitwig 2.4 is available to new users of Bitwig at purchase, where you will get a years worth of free upgrades or for existing users via their yearly update plan which costs 169USD