I've done a lot of spectral simulations in my career, and one issue that seems to crop up frequently is selecting a line of interest on a graph consisting of 1000s of lines and figuring out what it is by viewing waves of frequency, intensity, quantum number, other label, etc. For occasional use, putting a cursor on the line and reading the point number is sufficient to go find the entries in the respective waves, but for rapid perusal, I came up with this trick. It "links" the top graph to the top table (one can imagine other simple ways to select the relevent graph and table...the underlying function uses window names) so that moving cursor A on the graph will bring the same point to the top line of the to the table. The assumption being whatever waves are displayed in the table match the spectral lines (or other type of data) on a point-by-point basis (labels, quantum numbers, radiative lifetimes, linewidths, etc)

You can also imagine changing how the line is selected: use a mouse click event with a hit test, for example. I went with the cursor instead because I figured I'd want a visual cue on the graph that I selected the point I thought I had, so even with a mouse click based selection I figured I'd end up programmatically moving a cursor to the selected point. Your mileage may vary.

Just guessing the supported Igor version. The limiting feature is probably the named window hook; I'm not sure when these were introduced.

Menu "Graph Linker"
	"Link Top Graph and Table", LinkGraphToTable(WinName(0,1), WinName(0,2))
end
 
Function LinkGraphToTable(graphname, tablename)
	string graphname, tablename
	SetWindow $graphname, hook(csr) = HookGraphToTable, userdata(TableLink)=tablename
End
 
Function HookGraphToTable(s)
	STRUCT WMWinHookStruct &s
	Variable hookResult = 0
	string graphname, tablename
	switch(s.eventCode)
		case 7:				// CursorMoved
			tablename = GetUserData(s.winName, "", "TableLink")
			if (WinType(tablename) == 2)
				Modifytable /W=$tablename topLeftCell=(pcsr(A),-1),selection=(pcsr(A),0,pcsr(A),-1,pcsr(A),-1)
			else
				print tablename, "is missing, Delinking Graph"
				SetWindow $s.winName, hook(csr) = $""
			endif
			break
	endswitch
 
	return hookResult		// 0 if nothing done, else 1
End

To see how it works, copy and paste following code on the command line:

make /d /n = 10000 testX, testY
testX = enoise(100)
testY = exp(gnoise(1))
display testY vs testX
ModifyGraph mode=1
ShowInfo
make /t /n = 10000 labels
labels = num2char(mod(p,26) + 65)
edit testX, testY, labels

Select Graph Linker -> Link Top Graph and Table

and move the cursor around.