Could you post an example of what you are seeking? Is this a blurred edge for a picture in picture effect or are you referring to blurred edges for a crawling text title?
For blurred edges, besides fx Effects/Video /Transform/Edge Feather, also see fx Effects/Video/Advanced Adjustments/Vignetting.
Under Applied Effects Tab for editing the effect...
For Vignetting see
For Edge Feather see
Once you drag the effect from fx Effects into the Timeline clip, you will see the panel for the effect under Applied Effects Tab/
In this case, I have dragged Edge Feather and Vignetting into the same selected Timeline clip to demo the panels involved.
You should use one or the other.