I know it might be late to add to this topic but I too was getting annoyed with Halion 6’s library creator which is exacty how I found it.
I made a relatively simple instrument and discovered that whilst making a library for it (which incidentally, you only need to to if you are going to share your work with other HSSE users) the software only outright check about 10 or so criteria that will deny your media bay from listing your instrument.
I get the whole… make and instrument… save it… export it as a layer… load it into HS and save it as a program… My error didnlt liw in any of that.
I decided to read the output file from a successful library build that didn’t actually contain the instrument in the media bay and found a warning… one of my pictures was too large… I changed it (needed to be 90 by 60 pixels) and on rerunning the build function… there it was… library and instrument… all working fine. I didn’t change anythng else… just the picture size.
I guess, this is just a heads up to what others here may have already alluded to… it’s the small thngs that will frustrate you here. The slightest imperfection will simply manifest in something failing in your output. Halion 6 is just incredibly fussy…!
As a general rule, I don’t make libraries as I use what I turn my samples into myself so just drag the vstpreset into a HS slot and use it that way.