Question: How can I convert the Gaia-magnitude G (and G_ESTIMATE) into a V-magnitude? The solution probably can be found in the Gaia Data Release Documentation for Gaia's EDR3 ("Early Data Release 3"), specifically section 5.5.1, Relationships with other photometric systems, but I have to admit, that I can't make heads or tails of it.
Related Question: The question Relationships between G magnitude, Johnson V magnitude, and spectral type of stars? is related in that it wants to explore the relationship between G and Johnson-V. However, my separate question is not a "duplicate", because the other question has the relation between the magnitudes and spectral type as its focus (perhaps erroneously, shouldn't the relation be between a colour index and spectral type?).
Background: I am exploring the solar neighbourhood based on the paper The 10 parsec sample in the Gaia era (see the CDS-entry). Among other things I want to know the objects' respective brightnesses and what is visible to the naked eye (or a specific instrument). For this I want to use the "V"-filter (column "V" in the catalogue to the paper). A bit more than 50% of the non-planetary objects in the catalogue have a V-mag listed. Most of the remaining non-planetary objects (stars, low-mass stars, white dwarfs, brown dwarfs) have either a Gaia-magnitude G or an estimated Gaia-magnitude G_ESTIMATE. Therefore I need a way to convert G to V. The conversion probably not straight-forward since $G$ is a band covering wavelengths 330–1050 nm, and $V$ seems to cover only 470-700 nm.
Looking for: I need an equation I can use in a spreadsheet program to convert G/G_ESTIMATE to V. Is there one, or does conversion require more information than is given in the 10 parsec-catalog? Thank you for your help!