Just upgraded to 3.x from 2.10(>) and align has been made (or is setup by default) useless. It now only has “Image” as a relative option. What happened to “First Item” and the other (3 or 4) options?
??? I only align on Image 5-10% of the time. The rest I’m aligning various layers to other items in the project 
???
PS: Sorry if this was asked back when 3 was release. Searching didn’t return any hits based on “Align” or “First Item”
Since you can have several active Layers/Channels/Paths the “Relative to active something” options have become ambiguous.
Use Relative to picked reference object, click the layer/channel/path in the canvas (this will give it the corner squares,a d), and click the adequate align button in the tool options.
Generally it is as Ofnuts described, however there is one instance which provides unexpected results. (and it is the one I use the most)
A stack of layers, all the same size, same place. If only a few then just move them around a bit. That might not be practical for lots of layers.
The obvious jumbles the order: https://i.imgur.com/iTBjRCY.mp4
To keep the correct order reverse the layer stack as: https://i.imgur.com/eBxv0dA.mp4
best of luck
Thank you, all.
That doesn’t work for me (at least, I can’t get it to work for aligning things as I use it - left edge justified, centered, etc). Stupid to change what they had before as it worked perfectly, and I can’t see how removing a tried-and-true feature serves any purpose, but I won’t go into my millenial diatribe.
I reverted to GIMP 2, and will stay with that.
Again, thank you.
