开启了 org-pretty-entities 可以自动将一些 tex 命令转换成对应的符号，很好用，比如自动把 \alpha 显示成 α。
最近发现可以在 org-entities-user 里面自定义新的符号，例如我常用 ⊢ 和 ⊆ 在原来的设置里面不包含，可以自行添加显示：
这个变量会影响导出，所以建议好好看一下 docstring
(setq org-entities-user
'(("vdash" "\\vdash" t "⊢" "⊢" "⊢" "⊢")
("vDash" "\\vDash" t "⊨" "⊨" "⊨" "⊨")
("Vdash" "\\Vdash" t "⊩" "⊩" "⊩" "⊩")
("Vvdash" "\\Vvdash" t "⊪" "⊪" "⊪" "⊪")
("nvdash" "\\nvdash" t "⊬" "⊬" "⊬" "⊬")
("nvDash" "\\nvDash" t "⊭" "⊭" "⊭" "⊭")
("nVdash" "\\nVdash" t "⊮" "⊮" "⊮" "⊮")
("nVDash" "\\nVDash" t "⊯" "⊯" "⊯" "⊯")
("subseteq" "\\subseteq" t "⊆" "⊆" "⊆" "⊆")
("supseteq" "\\supseteq" t "⊇" "⊇" "⊇" "⊇")
("subsetneq" "\\subsetneq" t "⊊" "⊊" "⊊" "⊊")
("supsetneq" "\\supsetneq" t "⊋" "⊋" "⊋" "⊋")
("nsubseteq" "\\nsubseteq" t "⊈" "⊈" "⊈" "⊈")
("nsupseteq" "\\nsupseteq" t "⊉" "⊉" "⊉" "⊉")
("nsubseteqq" "\\nsubseteqq" t "⊈" "⊈" "⊈" "⊈")
("nsupseteqq" "\\nsupseteqq" t "⊉" "⊉" "⊉" "⊉")
("subsetneqq" "\\subsetneqq" t "⊊" "⊊" "⊊" "⊊")
("supsetneqq" "\\supsetneqq" t "⊋" "⊋" "⊋" "⊋")
("nsubset" "\\nsubset" t "⊄" "⊄" "⊄" "⊄")
("nsupset" "\\nsupset" t "⊅" "⊅" "⊅" "⊅")
("nsubseteq" "\\nsubseteq" t "⊈" "⊈" "⊈" "⊈")
("nsupseteq" "\\nsupseteq" t "⊉" "⊉" "⊉" "⊉")))
