When Ctrl/Cmd+clicking the first time (selecting a commit), this new commit should be shown. OK.
What should happen, when Ctrl/Cmd+clicking the second time (unselecting a commit)?

Try Ctrl/Cmd+P.

The portable bundle of SmartGit should work fine. The InnoSetup based installer checks for x64, because that is the executable format - it should prevent installation on 32 bit Windows. IMHO the processor emulation on Windows/ARM is suboptimal if it reports does not report x64 but executes x64 code.

Try setting the low-level property files.split.vertical to false.

If you mean the .deb file: this is not necessary, because installing the .deb file will create a menu item automatically.

Does your repository contain a .gitflow file in the root directory as stated in https://docs.syntevo.com/SmartGit/Latest/Git-Flow.html#git-flow-commands?

You have 2 options:
- use Reset Advanced or

- set the low-level property reset.default

Have you tried SmartGit 22.1 preview?

If you hide the Output view, an output dialog will be shown if the command failed. There you can select text easier.