Über dieses Add-on
Stylish v2.0.* and up (not tested nor supported on older versions)
Stylish-Custom Guide: https://choggi.org/wiki/stylish-custom
Forum Thread: https://forum.userstyles.org/discussion/2799/stylish-custom#latest
Customizable edit dialog (drag n drop)
Import/export styles and stylish-custom settings
Restores the !important button, Color/Site Rules menuitems, enable/update checks
Page button (left click for style page, right for edit page, it also posts the code. middle if you don't want to post code)
Style info listing with quick enable toggle (dbl-click to edit style, can also search within Styles, delete multiple styles)
Adds search/replace to edit dialog (ctrl+F, ctrl+R, and F3)
Press ! to type !important (can be changed in edit dialog)
Select and un/comment/merge lines of text
Preview/unpreview style changes without closing dialog
Stylish-Custom for Stylish v1.4.3:
There is also Stylish Editor Modified:
You could try having them both installed, but you are on your own for any issues/bugs.
ex/import can't be sorted.
when you update all styles from the manage window; you need to either close then reopen it or save a style to see changes.