With this add-on, you can easily increase or decrease the prefix number for the selected objects, you just need to select all the objects that you want to change and press the button!

You have 30 numbered objects and you want to add a new object in the middle without re-numbering them all?
Now you can!

To use this add-on, go the "Scene" panel, write the separator character that separate the number from the object name (for example: for the object - 'Cube.001', the separator will be '.'  and for the object 'Cube_001' the separator will be '_'),
now just press on the button that you require.

(In the next version it will also change the numbers of the bones)