Comment 14 for bug 172162

<off-topic>
> in the current state any hidden object forces the user to
> take a look on the XML editor

what about:
a) The preferences for 'Selecting' allows hidden / locked objects to be part of a 'Crtl+A' selection set (and when using 'Tab' or 'Shift +Tab').
b) You can access hidden / locked objects with the 'Edit > Find…' dialog. Once they are part of a selection set you can move them, change attributes, copy them etc. You just have no access to them with the mouse. You can search and select hidden images, move them to a separate layer and unhide them with 'Unhide All' ;-)
c) And finally - you can unhide / unlock all hidden or locked objects in the current layer with 'Object > Unhide All' and 'Object > Unlock All'.

But there are separate RFEs about an improved GUI for locked/hidden objects. ;-)
</off-topic>

What seems missing is a menu entry like 'Objects > Image properties': you can't get to that dialog even if you manage to select a hidden or locked image because it is only available in the context menu. You first have to use 'Object > Object properties…' to unlock/unhide the image and then 'context menu > Image properties'.