Simple image-editing program to add shapes/text to an image that are still editable after saving?
All the software I would normally recommend are probably out of scope considering your comments about Adobe Photoshop, and the fact you're looking for something more user-friendly and simple.

Since you just want to be able to annotate an image and then edit this again later, one option for this type of thing is to use MS PowerPoint (which you already have). 

I've shown many people over the years how they can use PowerPoint and most of them have been happy with the results, so give this a go before you dismiss it.

Using MS PowerPoint

One feature of MS PowerPoint 2011 and above is that you can group items on the slide and save them as a single image. So, you could do what you want as follows:


Insert the image into your PowerPoint slide.
Use shapes etc to draw arrows, lines, etc.
Use text boxes to add in your comments.
Format them as necessary (color, line weights, etc).
Select all items (i.e. the image and any shapes, etc.).
Right-mouse-click on your selection and go to Grouping > Group to group them together.
Right-mouse-click on the grouped items and select 'save as picture'.
Select from PNG, JPEG, GIF and BMP for the image format you want (you can also select PDF as an option).
Now also save your PowerPoint presentation.


And there you go - you've got yourself an edited (annotated) image you can use that is separate from the original file, and if you save the PowerPoint slide you have a way of going back and editing it again.

PowerPoint also gives you some pro editing features such as the ability to arrange items (e.g. Forwards, Backwards, Front, Back) as well as adding shadows, transparencies, etc. If you take the time to really get to know it, you'd be surprised what you can do.

I hope you don't mind, but I took the liberty of using your profile pic to do a quick edit with it in PowerPoint just to give you a taste of what's possible.