Before I retired I worked for a huge local council that tried for nearly 6 years to transition from MS Office to first StarOffice then OpenOffice many years ago... and gave up. Our Power Users just couldn't come to terms with the lack of scripting support, including documentation. The council went back to MS Office.
I can't help. You'll need
help.libreoffice.org and specialised OpenOffice/LibreOffice forums, not this VBS forum... nor any other Tek-Tips forum.
If you look for
Impress > Macros in the
LibreOffice wiki you'll see it has a grand total of 2 listed. Documentation is not LibreOffice's strong point, mainly because its developers are nuts'n'bolts, under-the-hood sort of people and the organisation has not yet attracted or yet seen the need for (or cannot afford) additional support personnel like documenters/tutorial writers.
You'll get a better understanding from articles like
Writing Macro in LibreOffice Impress – Getting Started and
Change Impress Layout at Runtime Using Basic Macro but, again, there's only 2 articles there.
There's just no correlation between Basic and VBA that I can see - let alone VBS - so you're going to have to start with the basics like
How to start writing macros in LibreOffice Basic and build from there.
To answer your question specifically, you are better off asking at
ask.libreoffice.org, not here You'll probably get better help there than from anywhere else.
Hope this helps...