If it proves cumbersome to repeatedly:
- group the selected shapes,
- attend to the options of the alignment inspector,
- and then ungroup,
you could assign a script to a keystroke or a Launchbar/Alfred trigger:
Code:
property pTitle : "Move selected graphics to centre of 1st canvas page"
property pVer : "0.01"
property pAuthor : "Robin Trew"
--CENTRE THE SELECTED BLOCK OF GRAPHICS ON THE FIRST PAGE OF THE OMNIGRAFFLE CANVAS
on run
tell application id "OGfl"
tell front window to set {oCanvas, lstSeln} to {its canvas, selection}
-- FIND THE CENTRE OF THE SELECTION(S)
-- Find horizontal and vertical minima and maxima of the selected shapes
set {rXMin, rXMax, rYMin, rYMax} to {10 ^ 6, 0, 10 ^ 6, 0}
repeat with oGraphic in lstSeln
tell oGraphic to set {{rX, rY}, {rAcross, rDown}} to {origin, size}
set {rRight, rBottom} to {rX + rAcross, rY + rDown}
if rX < rXMin then set rXMin to rX
if rRight > rXMax then set rXMax to rRight
if rY < rYMin then set rYMin to rY
if rBottom > rYMax then set rYMax to rBottom
end repeat
-- and derive an aggregate centre of the selected shapes
set {rMidSeln_X, rMidSeln_Y} to {(rXMin + (rXMax - rXMin) / 2), (rYMin + (rYMax - rYMin) / 2)}
-- GET THE X,Y DELTAS BETWEEN THE SELECTION(s) CENTRE AND THE PAGE CENTRE
tell oCanvas to set {rPageAcross, rPageDown} to page size
set {rDeltaX, rDeltaY} to {(rPageAcross / 2) - rMidSeln_X, (rPageDown / 2) - rMidSeln_Y}
-- TRANSLATE THE POSITION OF EACH SELECTED SHAPE
repeat with oGraphic in lstSeln
tell oGraphic
set {rX, rY} to origin
set origin to {rX + rDeltaX, rY + rDeltaY}
end tell
end repeat
end tell
end run