Is there any script to center right-aligned text/numbers inside every cell in every table?

Hi @KALSEL33703823ork9, you've got some ideas already, but here's another scripting approach. I've focused on (a) the selection vs the document, and (b) using findGrep to do the heavy lifting. I've also tried to show the workings so you can adjust yourself. For example, instead of justifying right, you could apply a paragraph style that was justified right.

Anyway, let me know if it helps.

- Mark

/**
 * @file Numbered Cells Align Right.js
 * 
 * Finds paragraphs inside table cells which
 * consist of numerical representations,
 * eg. 123 or 12.3 or -123 or (123) or (1,234.00)
 * It will not find currency symbols.
 * 
 * If a selection, it will try to process those item(s),
 * or if no selection, will process the whole document;
 * 
 * To adjust the find, look at the line that assigns
 * a string to `app.findGrepPreferences.findWhat`.
 * 
 * @author m1b
 * @version 2024-07-20
 * @discussion https://community.adobe.com/t5/indesign-discussions/is-there-any-script-to-center-right-aligned-text-numbers-inside-every-cell-in-every-table/m-p/14747317
 */
function main() {

    if (0 === app.documents.length)
        return alert('Please open a document and try again.');

    // reset grep
    app.findGrepPreferences = NothingEnum.NOTHING;

    // grep to find paragraphs which are numbers
    app.findGrepPreferences.findWhat = '^\\h*\\(?-?[\\d\\.,]+\\)?\\h*$';

    var doc = app.activeDocument,
        items = doc.selection.length > 0 ? doc.selection : [doc];

    itemLoop:
    for (var i = 0, item, found; i < items.length; i++) {

        // we want only specific items here
        var item = getParent(items[i], ['Document', 'Table', 'TextFrame', 'Story']);

        if (undefined == item.findGrep)
            // can't do findGrep on this, so move on
            continue itemLoop;

        // find paragraphs we want
        var found = item.findGrep();

        foundLoop:
        for (var j = 0; j < found.length; j++) {

            if (
                'Cell' !== found[j].parent.constructor.name
                || RowTypes.BODY_ROW !== found[j].parent.rowType
            )
                // we don't want this paragraph
                continue foundLoop;

            // make the change
            found[j].justification = Justification.RIGHT_ALIGN;

        }

    };

};
app.doScript(main, ScriptLanguage.JAVASCRIPT, undefined, UndoModes.ENTIRE_SCRIPT, 'Numbered Cells Align Right');

/**
 * Returns a parent of `item`, chosen
 * according to a list of types.
 * The order of types matters.
 * @author m1b
 * @version 2024-07-20
 * @param {PageItem} item - an Indesign page item.
 * @param {Array<String>} types - the desired types.
 * @returns {PageItem} - the parent page item.
 */
function getParent(item, types) {

    while (item.hasOwnProperty('parent') && item.parent) {

        for (var i = 0; i < types.length; i++)
            if (types[i] === item.constructor.name)
                return item;

        if (!item.parent)
            break;

        item = item.parent;

    }

};

Edit 2024-07-22: fixed typo in the script documentation.

If we are suggesting paid solutions - my tool will load texts from the tables, then can selectively style them / align. But it's PC only. 

Find&Change GREP would work "globally" - but only if texts you want to realign are ONLY in tables.

@KALSEL33703823ork9

Do you have a unique Char / Para Style already applied to the texts in Tables - that could be used to narrow the search?

Yes, there's my (not free) https://www.id-extras.com/products/centertablecolumns/ which does just that!

Maybe a better way, but this should work. 

app.activeDocument.stories.everyItem().tables.everyItem().columns.lastItem().cells.everyItem().texts.everyItem().justification = Justification.RIGHT_ALIGN;