Allow to replace a shape with a grouped shape from the draw.io scratchpad or a custom library

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• I have searched the issue tracker for a feature request that matches the one I want to file, without success.

Is your feature request related to a problem? Please describe.
I added a custom shape to my scratchpad, consting of several grouped shapes. I like to be able to replace shapes on the canvas with the custom shape (if possible). I guess that can be tricky, due to the fact that we are talking about a set of shapes instead of one shape (where the connection points are clearly defined). I also tried to do the same with a custom library, this didn't work out as well.

Describe the solution you'd like
Being able to replace existing shapes with a grouped subset of shapes.