Problem

Currently, pressing the Escape key while editing a cell immediately switches JupyterLab into Command Mode.
In many common editors, however, Escape is first used to clear any active cursor selection.
This difference can feel unintuitive: if a user has a selection active, pressing Escape may be expected to simply clear the selection rather than exit Edit Mode altogether.

Proposed Solution

• When a selection is active, pressing Escape should clear the selection.
• Only when no selection is active should Escape switch from Edit Mode to Command Mode.

One possible modification could be:
(jupyterlab/packages/codemirror/src/commands.ts)

export function simplifySelectionAndMaybeSwitchToCommandMode(target: {    dom: HTMLElement;    state: EditorState;    dispatch: (transaction: Transaction) => void;  }): boolean {    const arg = { state: target.state, dispatch: target.dispatch };    const preventDefault = simplifySelection(arg);-    if (target.dom.closest(ACTIVE_CELL_IN_EDIT_MODE_SELECTOR)) {+    if (!preventDefault && target.dom.closest(ACTIVE_CELL_IN_EDIT_MODE_SELECTOR)) {      // do not prevent default to allow switching to command mode      return false;    } else {      return preventDefault;    }  }

Note that the simplifySelection command returns false when the selection is already simple (i.e., no change was needed).

https://github.com/codemirror/commands/blob/6b76f57b07f115e604abf275d951b8f01d9ee982/src/commands.ts#L507-L517