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.

Do you mean environment variable support in the Command input field?

If you just have 1 commit selected, then the Changes view always shows the older part left and the newer part right. If 2 commits have been selected, the Changes view's title shows the IDs in the correct order.