I want help with selection

[rich2005]

There is a useful filter for extracting 'objects' in the gmic_gimp plugin. http://www.gmic.eu A bit overkill for just that function but a great plugin.

Not sure if you want total transparency or...what so refer to screenshots 

https://i.imgur.com/jS4XmzH.jpg
1. Add transparency  to the image Layer -> Transparency -> add alpha channel. 
Color -> Color to Alpha to remove white.
2. Using the Gmic plugin extract objects. Default values work with this one.

https://i.imgur.com/1NM83PT.jpg
3. That separates into individual small layers but in the same layout as original. Which might be enough for you.
4. Use the Align tool. Shift-Click on each 'object' to select all.
5. Align to left edge
6. Align to top edge

https://i.imgur.com/zNVZEL5.jpg
7. Use Image -> Crop-to-content to trim the image.
If you need to scale, Image -> Scale The original had no antialiasing so set interpolation to None.
8. For that single bar, manual fix. Copy from top layer, paste in bottom layer.

I am sure that will baffle you initially but please practice. Small gimp xcf image with layers attached.