Sometimes it's really difficult to align items, especially when you can't see the item you're placing in the same view as the item you want to place it in relation to, i.e.: placing a lamp above a table when you can't see the table because you need to look up to place the lamp.

It would be really convenient to be able to press a button to "Anchor" the item you're placing in place without fully placing it so you can take a step back and see if it's in the right position. Subsequently it'd be great to be able to "Nudge" that item around on the placement grid with the arrow keys (for example) while it's anchored as such to get the alignment just right.