View > Show Backdrop displays similar glyphs in the background. This makes it easier to keep your glyphs consistent.
Choose View > Show Backdrop to toggle the tool. Select a row in the list and use the arrow buttons to move around a glyph (hold Shift key for larger steps). To change the alignment use the segmented button in the bottom.
If you want to make permanent change to the standard database open the Backdrop folder (~/Library/Application Support/Glyphs/Repositories/Backdrop), right-click on Backdrop.glyphsReporter and choose Show package content. Then open Contents/Resources/glyphLib.py and make all the changes you want.