Please, add spectacle -E to the “open with” selector
hi, welcome.
you can easily add it yourself with the applications editor (right click on the app menu icon).
just include the -E in the command line box and give it a new name like Specacl(E) or something obvious.
then all you need to do is move it up on the file associations list so it appears near the top of the open with… menu for .jpg or whatever format you use for screen shots.
You can also use Photos (also known as “Koko”) which embeds the same editor.