In earlier versions of Obsidian (eg. v1.4) it was possible to have a plugin that adds decorations inside tables however this is no longer possible.
Reproduction
Clone the sample plugin
git clone https://github.com/obsidianmd/obsidian-sample-plugin.git
Replace main.ts with the following code.
import { syntaxTree } from "@codemirror/language";
import { RangeSetBuilder } from "@codemirror/state";
import {
Plugin
} from "obsidian"
import {
Decoration,
DecorationSet,
EditorView,
PluginSpec,
PluginValue,
ViewPlugin,
ViewUpdate,
WidgetType,
} from "@codemirror/view";
class EmojiWidget extends WidgetType {
toDOM(view: EditorView): HTMLElement {
const div = document.createElement("span");
div.innerText = "👉";
return div;
}
}
class EmojiListPlugin implements PluginValue {
decorations: DecorationSet;
constructor(view: EditorView) {
this.decorations = this.buildDecorations(view);
}
update(update: ViewUpdate) {
if (update.docChanged || update.viewportChanged) {
this.decorations = this.buildDecorations(update.view);
}
}
destroy() {}
buildDecorations(view: EditorView): DecorationSet {
const builder = new RangeSetBuilder<Decoration>();
const { from, to } = view.viewport;
syntaxTree(view.state).iterate({
from,
to,
enter(node) {
if (node.type.name.startsWith("list")) {
// Position of the '-' or the '*'.
const listCharFrom = node.from - 2;
builder.add(
listCharFrom,
listCharFrom + 1,
Decoration.replace({
widget: new EmojiWidget(),
})
);
}
if (node.type.name.startsWith("hmd-table-sep_hmd-table-sep-")) {
let candidate = view.state.doc.slice(node.from).iterLines().next().value;
const index = candidate.indexOf("-x")
if (index != -1) {
const listCharFrom = node.from + index
builder.add(
listCharFrom,
listCharFrom + 1,
Decoration.replace({
widget: new EmojiWidget(),
})
);
}
}
},
});
return builder.finish();
}
}
const pluginSpec: PluginSpec<EmojiListPlugin> = {
decorations: (value: EmojiListPlugin) => value.decorations,
};
export default class EmojiList extends Plugin {
onload() {
this.registerEditorExtension([
ViewPlugin.fromClass(
EmojiListPlugin,
{
decorations: (value: EmojiListPlugin) => value.decorations
}
)
]);
}
}
This should replace any list items or “-x” inside tables with the 
emoji.
Run the plugin (npm install; npm run dev) and enable the plugin.
Create an Obsidian file like the following:
- this is a list item
- list item 2
- list item 3
| | col1 | col2 | col3 |
| ---- | ---- | ---- | ---- |
| row1 | -x | -x | -x |
| row2 | -x | -x | -x |
In Live Preview mode (Setting > Editor > Default Editing mode), the decoration doesn’t show up in the table (however the list decoration still works). However in source mode, you are able to see the decoration in both the list and table.