It would be useful to use the hang baseline feature (documented here) for the Tibetan fonts. It would allow Noto to be displayed in several sizes on the same line keeping a correct Tibetan style. The current result is:

(from LibreOffice 5.2.3.1/Debian), while the correct result would be to keep the top strokes of the ཀ aligned. This won't work out of the box with my version of LibreOffice (I tried to change the value with Fontforge), I'll file a bug report to LibreOffice separately. Curiously, for fonts with a "tibetan baseline" at 0, the hang feature works fine in LibreOffice).