"I often find I need to write macros to do things that Excel can do out of the box. Sliding scales on charts, for example."
Please submit these to the Libre Office developers. If they're on github, you can do it in the form of an 'issue' with a request like "please implement the functionality as shown in this macro" or something.
Someone just might do it! Or it could end up in a macro library, and others will benefit.
THIS is how you "pay for" open source. Contribute something you don't mind giving away, something that could benefit everyone. It adds up, yeah, especially bug fixes or feature enhancements.