Smart indentation
Per-language auto-indent on Enter (block openers, matching-pair stanzas, closer re-alignment), plus smart backspace that clears a whole indent level in one press.
Enter does the right thing per language: it keeps the current line’s indent, adds a level after a block opener (braces, : in Python/YAML, do/then in shell, an open tag in XML/HTML…), and splits a matching pair into an indented stanza with the closer dropped below. Typing a closer ()]} or a keyword like end/fi/done) re-aligns the line to its opener.
Smart backspace removes a whole indent level in one press, and on a blank, auto-indented line, a single Backspace jumps back to the end of the previous line. The indent unit (tabs vs spaces) is inferred from the file.