How do I adjust the edge box when is comes to custom cropping it?

I only have the option of cropping my animation automatically but it won't let me adjust the edges custom

Edit your frames in a dedicated image edition software. Then import them in Construct.

Or consider adding your request on the suggestion platform - construct.net/en/forum/construct-3/general-discussion-7/where-to-report-bugs-post-sugg-128538