You have two options to choose from.
### Option 1 (Easiest)
1. Turn off Sync UV Selection.
2. Open the N-panel (sidebar) in the UV Editor.
3. Select the elements you want to align.
4. Select the Vertex by Vertex mode.
5. Click Align.
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### Option 2
1. Turn on Sync UV Selection.
2. Make sure Sticky Selection Mode (located right next to the Selection Modes: Vert, Edge, Face in the UV Editor) is set to Shared Location.
3. Select the elements you want to align.
4. Select the Vertex by Vertex mode.
5. Click Align.