You can "Silence Selected" under the Process menu to silence all currently selected slices. (Shift click to select multiple slices) This will prevent the silenced slices from being exported.
Single sample is more complicated:
Enable "Transfer as 1 Sample" by either clicking the button displaying a looped waveform or using the menu option under the Process menu.
Set the loop region by selecting the right-clicking and using the "Set X Locator" or "Set Loop Around Slice" to select the slice or sequential group of slices that will be exported as a single wav.
Export. That's a single slice export. Disable the "Transfer as 1 Sample option before using again as normal.
-thync
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Cuz you aint seen through my eyes
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