For single-line diagrams: QElectroTech — free, designed exactly for electrical one-line drawings, exports SVG/PDF. For PLC sequence logic: Mermaid (sequenceDiagram in a .md, renders anywhere) is the fastest hack, and mingrammer python "diagrams" package if you want diagrams from code/CI. My workflow: text the sequence in Mermaid first, reviewers comment on it, then it becomes the source of truth instead of a pretty image you will redo anyway.
For single-line diagrams: QElectroTech — free, designed exactly for electrical one-line drawings, exports SVG/PDF. For PLC sequence logic: Mermaid (sequenceDiagram in a .md, renders anywhere) is the fastest hack, and mingrammer python "diagrams" package if you want diagrams from code/CI. My workflow: text the sequence in Mermaid first, reviewers comment on it, then it becomes the source of truth instead of a pretty image you will redo anyway.