jupyterlab/style/breakpoints.css

/*-----------------------------------------------------------------------------
| Copyright (c) Jupyter Development Team.
| Distributed under the terms of the Modified BSD License.
|----------------------------------------------------------------------------*/

.jp-DebuggerBreakpoints-body {
  padding: 10px;
}

.jp-breakpoint-marker {
  position: absolute;
  left: -34px;
  top: -1px;
  color: var(--jp-error-color1);
}

.jp-breakpoint-line-highlight {
  background-color: var(--jp-warn-color0);
}

.CodeMirror-gutter-wrapper::after {
  content: '●';
  color: var(--jp-error-color1);
  opacity: 0;
  position: absolute;
  left: 3px;
  top: -1px;
}

.jp-Notebook
  .jp-mod-editMode
  .jp-CodeCell.jp-mod-selected
  .CodeMirror-gutter-wrapper:hover::after,
.jp-Editor.jp-mod-focused
  .CodeMirror:not(.jp-mod-readOnly)
  .CodeMirror-gutter-wrapper:hover::after {
  opacity: 0.5;
}