A meaningful name.

Why not use a speaking name for the branch?

Right-clicking a group in SmartGit 19.1 there also is a "Add Group" menu item.

Since the beginning you can move repositories to groups using the context menu. Please also try SmartGit 19.1.

Ah, you are right. For the Create Tag dialog there is the completion. But independent of this, you can select from the combobox popup and then modify.

Please try Ctrl-Space.

The prefix, e.g. "fixup! " can be configured with the low-level property log.useCommitMessage.prefix.

Please take a look at https://www.syntevo.com/blog/?p=4751.

For what language?

One further clarification: what should happen if you paste some text containing tab characters?