The definition of "shape" is in line 5778. It contains the shapes, which are listed in the description.
An addition to the text in section 11.1 <chart:chart> is not necessary. The gray part should be generated automatically from the schema, isn't it? Nevertheless, the generated text should be
The <chart:chart> element has the following child elements: <chart:footer> 11.2.3, <chart:legend> 11.3, <chart:plot-area> 11.4, <chart:subtitle> 11.2.2, <chart:title> 11.2.1, <dr3d:scene> 10.5.2, <draw:a> 10.4.12, <draw:caption> 10.3.11, <draw:circle> 10.3.8, <draw:connector> 10.3.10, <draw:control> 10.3.13, <draw:custom-shape> 10.6.1, <draw:ellipse> 10.3.9, <draw:frame> 10.4.2, <draw:g> 10.3.15, <draw:line> 10.3.3, <draw:measure> 10.3.12, <draw:page-thumbnail> 10.3.14, <draw:path> 10.3.7, <draw:polygon> 10.3.5, <draw:polyline> 10.3.4, <draw:rect> 10.3.2, <draw:regular-polygon> 10.3.6 and <table:table> 9.1.2.
I support this feature request. AOO and LO already support the drawing objects <draw:caption>, <draw:custom-shape>, <draw:ellipse>, <draw:frame> with draw:text-box, <draw:line>, <draw:path> in UI as freeform line, <draw:rect>.
The other types of objects mentioned in the proposal are not supported by AOO and LO. It might be subject of discussion, whether these should be allowed too.