I found Voynich characters in a 14th century Arabic manuscript

[nablator]

Is it possible that this is some kind of proto-Voynichese encoding? What do you think?

These are examples of magical "caractères à lunettes" (French, not sure how to translate properly; it means characters that look a bit like glasses, it's just a structural analogy, no deep meaning) that are found in magical manuscripts such as the Latin Picatrix, a translation from the original Arabic. See Mary D'Imperio The Voynich Manuscript: An Elegant Enigma.

It is unlikely that the gallows are related. The resemblance may be coincidental: most of the Voynich glyphs look like some known letters, ligatures, numerals and symbols.

The VMS is not similar to books of magic of any type: Arabic and Salomonic magic books have talismans, incantations and these magical characters with loops. There are again some superficial resemblances with circular diagrams but not enough to call any of them a match.