Under Manjaro Linux, in Firefox 47.0 with It’s All Text 1.9.2, the button Open in external editor is completely missing when editing a user style for Stylish (V2.0.6). Where the button is supposed to appear, between the button Paste and the checkbox Line wrap, there is a big empty space instead.
However, it appears as it should in Pale Moon 26.3.0 using the same versions of these extensions.
I've found a solution! By following the 2nd and 4th comment under this issue, I opened about:config, looked for extensions.stylish.editor and changed its value from 0 to 1. Now the button appears in Firefox 49 just like in Pale Moon.
Under Manjaro Linux, in Firefox 47.0 with It’s All Text 1.9.2, the button Open in external editor is completely missing when editing a user style for Stylish (V2.0.6). Where the button is supposed to appear, between the button Paste and the checkbox Line wrap, there is a big empty space instead.
However, it appears as it should in Pale Moon 26.3.0 using the same versions of these extensions.