there are a lot of things that need to be cleaned up in shot cut.
i will not list ALL of them.
Just a few:
the blur effect and some other effects should have a specific area on the clip, not having to create a new clip, line it up, cut down to the blur area, crop it down, size and position it, and finally blur it. in summary, make it so the blur only blurs a selected section of a clip, simmilar to how the text size and position is.
This is not necessary. Use the filters in this order:
Mask: Simple Shape or Mask: From File
In the future there will be more step 1 mask definition options, but already this is more flexible than adding a masking rectangle to each filter. After step 1 you can use other filters to further shape or preview the alpha channel. At step 2, you can use any number of additional filters for the same mask.