Apparently the "new" notes tool broke the Mac's ability to add diacritical marks in notes. This isn't new to L9, but I don't know if this bug received much attention or was noticed by FL. It looks like this has been an issue since the notes tool was released (beta in L7, release in L8).
The ability to add diacritical marks on Mac is typically accomplished by long pressing a vowel. In the clippings tool, for example, the user can still do this:

Can someone at Faithlife take a look at this issue and report back?
EDIT: Here are some previous posts:
https://community.logos.com/forums/p/184953/1065415.aspx#1065415
https://community.logos.com/forums/p/191435/1104239.aspx#1104239
https://community.logos.com/forums/p/195506/1130451.aspx#1130451
https://community.logos.com/forums/p/198513/1151056.aspx#1151056