If you find that you’re missing nodes in the render tree Preset Manager, then check the Softimage install folder. In particular, check
In a working Softimage installation, like mine , the content of the Preset Manager is determined by spdl/mi files in those folders (and perhaps others too).
For example, if I delete mia_lens_bokeh.spdl from $XSI_HOME\Application\phenolib\spdl\mibase, then Bokeh (mia) disappears from the render tree preset manager. If I put it back, and refresh the preset manager, the shader re-appears.