I am trying to create a new command that will replace text with a blank line to write on. Essentially, the lovechild of, \underline and \phantom if it can be toggled on and off that would be even better but I seem to have a misunderstanding of how macros work in latex.
My crappy code is below
\newcommand{\rmv{}}{\Underline{\phantom{}}}
You're macro needs to know what text you want in the gap, so it needs an argument. The syntax to pass argument to the new macro is
\newcommand\macroname[number of arguments]{use the argument with #1 etc.}
\documentclass{article}
\newif\ifgaps
\gapstrue % comment/uncomment to toggle
\newcommand{\rmv}[1]{%
\ifgaps%
\underline{\phantom{#1}}%
\else%
#1%
\fi%
}
\begin{document}
test \rmv{test} test
\end{document}
(to automatically create two versions of your pdf with and without the gaps, you could use something similar to https://topanswers.xyz/tex?q=583 )