Two obvious questions remain:

1. What about the appearance of this general type of glyph in other texts? Do they exist? If so, are there any clues there?

2. And if so, what about their meaning?

We can for instance in Ga3-10 see ragi and tea when the Full Moon ideally should have been in NOVEMBER 28:

... The correspondence between the winter solstice and the kali'i rite of the Makahiki is arrived at as follows: ideally, the second ceremony of 'breaking the coconut', when the priests assemble at the temple to spot the rising of the Pleiades, coincides with the full moon (Hua tapu) of the twelfth lunar month (Welehu). In the latter eighteenth century, the Pleiades appear at sunset on 18 November. Ten days later (28 November), the Lono effigy sets off on its circuit, which lasts twenty-three days, thus bringing the god back for the climactic battle with the king on 21 December, the solstice (= Hawaiian 16 Makali'i). The correspondence is 'ideal' and only rarely achieved, since it depends on the coincidence of the full moon and the crepuscular rising of the Pleiades ...

And from such glyphs as Aa4-18 I think it is probable that the three vertical lines with a roof above and a great mata at top right were used to signify hau tea.

Then we have Ha1-28--29 (with parallels in P and Q).

And we have Small Washington; first Ra6-18 in the text parallel to Ga3-10 / Ka4-4 etc. Then there are Ra7-109 and Ra8-103, which glyphs (with surroundings) - together with Ra3-122--124 - indicate close similarities with the text we are studying in Tahua.

Those are the only comparable glyphs which readily will be found in the rongorongo texts. (But the Santiago Staff I will not look at until I have worked through all the other texts enough to feel stability in my readings.)