In PTE AV Studio 12 we have added a frame interpolation option (dissolve) when slowing down a video object.
Objects and animation editor > Properties tab > Trim and Adjust speed button > Interpolate Frames.
It works in real time, including in EXE shows and video export.
Please see the example for 7% speed (0.07x) with frame interpolation and without:
slo-mo.mp4