Basic editor functions to copy events from one animation clip to another. No guarentee of functionality, please only use with backups or under source control.

AnimClipEventCopy.cs

using UnityEngine;
using UnityEditor;
using UnityEditor.ShortcutManagement;

public static class AnimClipEventCopy
{
	static AnimationClip sourceClip;

	[Shortcut("AnimClipEventCopy/Set Source Clip")]
	public static void CopyEvents()
	{
		if(Selection.objects.Length != 1)
		{
			SceneView.lastActiveSceneView.ShowNotification(new("Select one animation clip to copy from."));
			return;
		}

		if(Selection.activeObject is AnimationClip clip)
		{
			sourceClip = clip;
			SceneView.lastActiveSceneView.ShowNotification(new($"Source clip set to: {clip.name}"));
		}
	}

	[Shortcut("AnimClipEventCopy/Paste Events to Clip")]
	public static void PasteEvents()
	{
		if(sourceClip == null)
		{
			SceneView.lastActiveSceneView.ShowNotification(new("No source clip to copy events from."));
			return;
		}

		if(Selection.objects.Length != 1)
		{
			SceneView.lastActiveSceneView.ShowNotification(new("Select one animation clip to paste into."));
			return;
		}

		if(Selection.activeObject is AnimationClip clip)
		{
			AnimationUtility.SetAnimationEvents(clip, sourceClip.events);
			SceneView.lastActiveSceneView.ShowNotification(new($"Copied events from {sourceClip.name} to {clip.name}"));
		}
	}
}