UPDATE: There is much better way of doing this, by using Windows Enhanced Metafile instead of Scalable Vector Graphics.
When making my custom Nutanix stencil package I ran into problems with shape sizes. Larger shape sizes increase the time to pull the shape from stencil to drawing. The more complex shape (with multiple sub-shapes) you have the larger it will be. Some of my original Nutanix shapes became so large that it took few minutes to pull shape into a drawing. Fortunately there is a way to fix this situation. The main goal is to collapse all sub-shapes into one shape or image and to get rid of unnecessary shapesheets and data associated with sub-shapes. To use this method you will need open source program called “lnkscape“ In Visio ungroup complex visio shape until there are no groups. select all the required objects save as “Scalable Vector Graphics”
In lnkscape new image opens in lnkscape (or open with lnkscape if *.svg filetype is associated with some other program) select image drag image from box surrounding the new image copy image to clipboard (CTRL-C)
In Visio paste image from clipboard (CTRL-V)
As end result most of the details are still shown, but there are no separate shape sheets for each picture component or sub-shape, leading to much lower file size and reduced shape placement times.