How to enter the original characters of “Markup language” in Math

[渣渣叮]

In LibreOffice, when i type

{C/C_RE} over {L/L_RE}

What I want is

Here are a few implementations I tried that were not good enough compared to the original implementation

L_{RP}

L_{“RP”}

L_{italic"RP"}

L_{R{P}}

L_{nospace{RP}}

[EarnestAl]

So not { C/C _italic "RE"} over {L/L_italic"RE"} ?

[mikekaganski]

Cannot type formula V_in : Librewriter 6.3.4.2

I want to type equation V_in in writer but it shows question mark instead of “in” Could anyone help [image description] Thank in advance attapon

Or rather the same text as FAQ.