Steps how to reproduce with installation of unofficial (by wg9s) De SeaMonkey 2.53.2 beta 1 pre Mozilla/5.0 (NT 6.1; Win64; x64; rv:60.0) Gecko/20100101 Firefox/60.0 Build 20200131130001 (Default Classic Theme, newly created User Profile) on German WIN7 64bit:

1. Launch Browser

2. Open Bookmarks Panel in Sidebar

3. on a bookmark entry: ˋRightclick → New Folderˊ
   » Expected: Dialog opens with input fields for folder name and comment

   Actual: Input fields are missing 😥

Additional Information

a1) Already reproducible with unzipped installer of unofficial (by wg9s) De SeaMonkey 2.53.2 beta 1 pre Mozilla/5.0 (NT 6.1; Win64; x64; rv:60.0) Gecko/20100101 Firefox/60.0 Build 20200131130001 (Default Classic Theme, newly created User Profile) on German WIN7 64bit
a2) Was still ok with unzipped unofficial (by wg9s) De SeaMonkey 2.53.1 (NT 6.1; Win64; x64; rv:60.0) Gecko/20100101 Firefox/60.0 Build 20191229130005 (Default Classic Theme) on German WIN7 64bit
a) Appeared with 2.53.2?
b) Also affected: ˋbookmarks → edit bookmarksˊ

Sorry was caused by a bad patch still in review. Latest version of the patch fixes it but wait till tomorrow. Bills current 2.53 x64 Windows build 2020-02-04 06:00 is bad.