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This is default behavior for popup menus and can't be changed. Maybe it helps to set the system property log.dragAndDrop.compact to false in the preferences to get back the old dialog.

Err, the compare is invoked with the HEAD and working tree file contents. Isn't that what you actually want to do - except that you just want to see it in the Changes view, whereas this work-around is about the separate Compare window?

To open a compare between HEAD and working tree (so you can edit it) for a file with staged changes, please select this option in the preferences.

Please use the normal Compare which supports it.

If the files are changed, but should be treated as unchanged, please select the files and invoke Local | Toggle "Assume Unchanged".

Already works: The first line in the commit message is your title, the third and following lines are the description.

You can open multiple repositories inside the same window by selecting all repositories, right-clicking and selecting Open. To add multiple local repositories, either use drag and drop or Repository > Search for Repositories.

Why don't you select such a font in the preferences?

Can be changed in SmartGit 18.1 in the "Low-level Properties" section of the preferences.