You can use some LISP tools that ensure that its loaded at startup.
Yes, on_start.lsp is a good place to check and load partial cui from.
You can make use of a S::Startup function to do those checks. e.g.Code - Auto/Visual Lisp: [Select]
(CCL-LOADMENU "CCL-EXTRAS" "CCL-Extras-BCAD.cui") ; Load CCL Menu if not already loaded )
CCL-LOADMENU is a function that checks if a given menugroup is loaded, and if it isn't loads it.Code - Auto/Visual Lisp: [Select]
; CCL-LOADMENU ; Load menu will check to see if the given Menu group is loaded. ; If it isn't, then it will be loaded ) )
Yet to update for V24 but we have a example setups for BricsCAD here that includes this
https://www.cadconcepts.co.nz/resources/bricscad-sample-setup
Fun fact for BricsCAD. the S::Startup function can be called multiple times from any lisp file set to autoload, such as on_start.lsp and on_doc_load.lsp. Can even be added to .mnl files.