You already can select a previous commit message. What about prefixing it (optionally) with "Fixup! "?

Just for curiosity: do you use the fixup! prefix to prepare amending a commit using interactive rebase?

I would not use a button - it's too heavyweight - but maybe an entry in the Select popup or the control+space popup?

SmartGit 18.2 preview already contains some Git-LFS commands. What further ones you are missing?

Will be implemented in build 13070.

The external application configured on the "Tools" page ("external tool") only is launched if you invoke it explicitly. Double clicking a modified file will use the matching tool from the "Diff Tools" page ("diff tool"). For an "external tool" the output should be passed to the stdout or stderr channel and use UTF-8 encoding. If there is no "Print Git Version" default external tool for you, please click "Re-Add Defaults".

Regarding SmartSynchronize: no, SmartSynchronize performs the diff, so you would need a script (configurable as "diff tool") that first converts the binary file to a text format and then let SmartSynchronize (or any other text file compare) do the diff display.

You need to select the option "Show output and wait until finished" in the external tool configuration dialog, similar to the "Print Git version" default external tool.

There is no way (yet) to get it displayed in the Changes tab. But you can invoke the script as a external tool upon request which is configured to show the command's output.

Have you tried SmartGit 18.2 preview from https://www.syntevo.com/smartgit/preview?

I like this idea because it could provide the linear history of the Journal in the Log window.

So you only would need the directory tree to filter out the displayed files - or do you also would like to perform commands on this directory level?