Just put this in a css snippet:
.CodeMirror-cursor,
div.CodeMirror-cursor,
.cm-fat-cursor,
.cm-animate-fat-cursor,
.cm-fat-cursor-mark,
.cm-cursor{
visibility: visible !important;
}
First seen here: https://forum.obsidian.md/t/options-to-modify-cursor-style/1091/4.